The 'Dripping Pen' greeting card and cipher were purportedly mailed virtually alongside the 'Bus Bomb' letter, on November 8th and November 9th 1969 respectively. The postmark on the 'Dripping Pen' card envelope is less than clear in many reproductions, but there may be a better version available somewhere online. However, there is something rather out of place regarding this Zodiac communication, particularly when one compares it to the 'Bus Bomb' letter postmarked just one day later.   

The Zodiac wrote his victim count using months of the year: "Des, July, Aug, Sept, Oct = 7," but in his next 'Bus Bomb' communication he adds "This is the Zodiac speaking up to the end of Oct I have killed 7 people. I have grown rather angry with the police for their telling lies about me. So I shall change the way the collecting of slaves. I shall no longer announce to anyone. When I committ my murders, they shall look like routine robberies, killings of anger, + a few fake accidents, etc."
Why is the killer informing us he has killed seven people up to the end of October, when he has made this plainly obvious in the 'Dripping Pen' card by addition of the last entry as "Oct," meaning October. If the Zodiac Killer had murdered anybody in November, then surely the total would be 8 victims, with November added to the list of months. The killer further states "I though(t) you would nead a good laugh before you hear the bad news. You won't get the news for a while yet." But we didn't hear of any bad news before he mailed the Melvin Belli letter on December 20th 1969, or for months thereafter. 
This may be because we had already heard the bad news, and the 'Dripping Pen' card was intended to be mailed slightly over a month earlier.
Mail can go astray from mailing to being postmarked, however, that avenue will not be explored here.
It seemed unusual for two such prominent communications to be sent either in tandem, or one day apart. The Zodiac Killer had obviously invested a lot of time crafting a new and innovative cipher, after becoming aware his first cipher had been cracked in a matter of days, and announced in the San Francisco Chronicle on August 9th 1969. So, after investing time and energy into his new masterpiece, it seemed strange he would take the shine and emphasis away from this new cipher, by tying it alongside the rather lengthy 'Bus Bomb' letter about the murder of Paul Stine on October 11th 1969 and his exploits in the park.
The 'Dripping Pen' card and cipher could have been mailed two weeks later to maximize impact. The context and choice of card, if chosen for purpose, also makes little sense. The message on the purchased greetings card read "Sorry I haven't written, but I just washed my pen."  The Zodiac Killer, however, had written only 27 days earlier, when he mailed the October 13th 1969 Paul Stine letter containing the swatch of bloodied shirt. The supposed bad news we were supposed to get also never materialized, and in addition, he would repeat the month of October just one day later, reminding us of seven victims claimed, as if our attention span only lasted 24 hours. All these factors place this correspondence and its contents curiously out of place. ​

We will attempt to put this card chronologically in its rightful place, where its contents can be understood. 
The wording "Sorry I haven't written, but I just washed my pen,"​ if this card was chosen carefully, seems to imply the killer had not written to the newspapers for a while-  longer than 27 days.
The Zodiac Killer prior to the October 13th 1969 Paul Stine letter, had not written to the newspapers since August 4th 1969, when the 'Debut of Zodiac' letter arrived at the San Francisco Examiner. That is over two months. It is longer regarding the San Francisco Chronicle, of over 10 weeks. This card now makes more sense. But why would the dripping pen (possibly red in color) be relevant to the Zodiac. 
On September 27th 1969, Bryan Hartnell and Cecelia Shepard were enjoying a pleasant picnic at Lake Berryessa when a knife-wielding man approached wearing an theatrical executioners costume, brutally stabbing the young couple 16 times in their back and abdomen. The assailant's hand or glove would have been covered in blood. Minutes later he wrote on the car door with a pen: Vallejo 12-20-68, 7-4-69, Sept 27-69 -6:30 by knife.
The pen would have been covered with blood. What better time to ironically proclaim in your next correspondence "Sorry I haven't written, but I just washed my pen," as if to imply he was the responsible for the callous attack and murder of Cecelia Shepard just days earlier, and was washing the blood from his pen. The author of the 'Dripping Pen' card further added "Could you print this new cipher in your frunt page? I get aufully lonely when I am ignored, so lonely I could do my Thing."
The Zodiac Killer, like most serial killers, don't have horns growing from their head- they go largely unnoticed and blend into society. The Zodiac Killer was certainly searching for notoriety, as opposed to the loneliness he experienced in everyday life. What better way, than to dress up in an executioners costume and do his "thing." 

The 'Dripping Pen' card would sit nicely between the Lake Berryessa attack and the murder of Paul Stine, had it been mailed sometime around September 30th 1969. The text on the card would then make further sense in respect to the month of October and the wording "I though(t) you would nead a good laugh before you hear the bad news. You won't get the news for a while yet."
The seventh victim was to become Paul Stine (or another taxicab driver) in San Francisco. He had already earmarked his next murder, and this was the "bad news" we were soon to receive. The addition of the month of October was the precursor to death, and unlike his previous attacks where he had to search out victims- in San Francisco they would literally come to him.
But why wasn't the 'Dripping Pen' card mailed after the Lake Berryessa attack?, assuming the communication didn't go astray from posting to postmark.
The Zodiac Killer likely had his ego dented after Donald Gene and Bettye June Harden cracked his 408 cipher in a matter of days. He may have began developing his more challenging cipher immediately in response, or at the very least sometime in August or September. 
The Zodiac Killer chose the greetings card in respect to the Lake Berryessa stabbings, for which he could have then attached his cipher and mailed it. But something changed.
​Did he want to revise or add to his cipher to incorporate the attack by the lake? Some have suggested the cipher may have been separated into two halves. Did the killer originally encipher a banal message, much like his original code, and wanted to completely redesign it. The intended murder at Presidio Heights was looming, and the killer was planning ahead. The cipher and card may have been placed on the back-burner. 
On October 11th 1969, taxicab driver Paul Stine was murdered in Presidio Heights. The killer mailed a piece of the taxicab driver's shirt two days later, and followed up with more details on November 9th 1969 about his excursion into the park. 
In between the October 13th 1969 Stine letter and November 9th 1969 'Bus Bomb' letter, the killer may have finalized his cipher, unable to replace the 'Dripping Pen' greeting card with an identical or relevant card, and with the Lake Berryessa attack cooling, mailed off both communications in unison. He stated we wouldn't "get the news for a while yet," totally negating the message he delivered one day later, that "I shall no longer announce to anyone when I committ my murders." Seemed like a quick change of heart. The card choice still made sense to him, if not us at this juncture, but the message inside now appeared chronologically repetitive in respect to the 'Bus Bomb' letter and the intended "bad news" had already occurred, although not apparent to the reader, so the threat still remained. 

Desert Sun Newspaper -November 10th 1969: Arsenic Is Found In Soft Drink MARTINEZ (UPI)-- 'A young schoolteacher who received threatening telephone calls for 10 days thought the caller was a crank who was pretending to be the Zodiac killer. But police took the threats seriously after 24-year-old Daniel Williams found a lethal dose of arsenic in a bottle of soft drink in his refrigerator. Williams, a teacher at Salesian High School in Richmond, told police the caller talked of how he intended to kill several persons, then last; Sunday said: “You’re the dead duck.” Williams went out and when he returned home found someone had pried open the screen on a back door. However, a police search showed nothing was missing. But after the officers left and Williams took a drink from a bottle of opened soft drink in his refrigerator, he found it tasted “metallic” and immediately spit it out. Police reported Friday that the bottle contained more than enough arsenic to kill a human being. Williams said the caller identified himself as the still sought Zodiac killer of five, but police discounted the idea. The caller would “sob and complain of headaches.” Williams said, and on one occasion said he had gone to a Martinez school in search of victims but left when he found police there. Williams said the caller told him: “I’m too smart for them.” link
The San Francisco Chronicle ran an article on the same subject on November 8th 1969, stating "The string of sadistic calls began on October 23rd. On one occasion, the caller told Williams he had gone to a Martinez school in search of victims but had left when he found police there. Another time, the teacher said the caller, whose voice he described as muffled as if speaking through a handkerchief, said he was going to "kill the lady in the blue house."  
The arsenic laden drink was discovered on November 2nd 1969. This may not have been the Zodiac Killer, however this threat was seemingly backed up. 
The article ran in the San Francisco Chronicle on November 8th 1969, so if this was the Zodiac, he may have been unaware at the point he mailed the 'Dripping Pen' card on November 8th, on whether his deadly attack had been successful. He mailed the "poison pen" letter on the same day and declared "I thought you would need a good laugh before you hear the bad news. You won't get the news for a while yet." Clearly, had Daniel Williams died from the poisoning, he may not have been discovered immediately. The style of attack would also conform to Zodiac's new declaration on November 9th, in that "I have grown rather angry with the police for their telling lies about me. So I shall change the way the collecting of slaves. I shall no longer announce to anyone. When I committ my murders, they shall look like routine robberies, killings of anger, + a few fake accidents, etc".     
The threatening phone calls and attempted murder of this high school teacher would precede the second cipher offering from the Zodiac. An offering accompanied by what could be interpreted as a "poison pen" letter. The Zodiac Killer's first cipher was cracked in a matter of days by Donald Gene and Bettye June Harden. Don Harden began teaching at North Salinas High School in 1960.  

There is slim chance this was Zodiac, but it doesn't hurt to explore every angle.
Martinez and Richmond, California, where Daniel Williams lived and worked are direct routes from Vallejo and Benicia through to San Francisco. The threatening caller stated he was going to "kill the lady in the blue house." So if the caller was Zodiac, however small the likelihood, what is the reasoning behind this threat, and was he familiar with the woman or the area in question.
The famous "blue house" is situated in the Castro District at 3841 18th Street, San Francisco, near Haight-Ashbury and the Golden Gate Park. It is 3.4 miles southeast of the October 11th 1969 murder of Paul Stine, a month earlier.
It was memorialized in music by French singer Maxime Le Forestier in 1971, inspired by his time living in the blue house with a hippie commune called "Hunga Dunga."
'Maxime Le Forestier spoke of the house where everyone was welcome, where Tom, Phil and Psylvia lived. The house was in fact home to the Hunga Dunga commune, and several of the people mentioned in the song still live in the Bay Area'. Mission Local. 
Could Daniel Williams have been Zodiac's intended eighth victim, and was the 'Bus Bomb' letter on November 9th 1969, stating "This is the Zodiac speaking up to the end of Oct I have killed 7 people" so precisely, indicative that an eighth victim was yet to be discovered, somewhere between October 31st 1969 and the date of this letter. 
The fact that Zodiac made a point of highlighting the "end of Oct" in the Bus Bomb letter, rather than just stating "to date I have killed 7 people" is extremely suggestive that we hadn't "heard the bad news yet".  

http://www.zodiacciphers.com/zodiac-news/skeleton-in-the-closet

On the 'Dripping Pen Card' mailed on November 8th 1969 the Zodiac left us his running victim count, but this time he provided us several pointers by displaying the months. He wrote "Des, July, Aug, Sept, Oct = 7."  We know of Lake Herman Road (2) in December, Blue Rock Springs Park (1) in July, Lake Berryessa (1) in September and Presidio Heights (1) in October. That is five murders out of the seven he was claiming. That meant he was indicating either two murders in August, or just one in August and another in either of the other months. One consideration was the murder of Cheri Jo Bates on October 30th 1966, that he would belatedly claim in a future correspondence. However his statement in the November 9th 'Bus Bomb' letter is telling: "This is the Zodiac speaking up to the end of Oct I have killed 7 people." This likely meant "This is the Zodiac speaking up to the end of Oct 31st 1969 I have killed 7 people. This doesn't necessarily rule out the Cheri Jo Bates murder, however without proof this is a Zodiac murder, or a murder under the umbrella of Zodiac, it is a curious statement.
Why did the Zodiac Killer specify the end of October, when his most recent murder by all accounts was the brutal slaying of Paul Stine on October 11th 1969. This could be interpreted as a sixth murder in August, and a seventh murder between October 11th 1969 and October 31st 1969. He would expand in his correspondence "I thought you would need a good laugh before you hear the bad news, you won't get the news for a while yet."  In view of his 'Bus Bomb' letter declaration that he would "change the way the collecting of slaves. I shall no longer announce to anyone. When I committ my murders, they shall look like routine robberies, killings of anger, + a few fake accidents, etc," this seventh murder may have been committed in the latter two thirds of October, detailed in the total, but not elaborated upon, and the suggestion that we wouldn't get the bad news for a while was somehow related to how or where the person was killed.     

There is however a completely different alternative, bringing into play the Melvin Belli letter on December 20th 1969. This correspondence stated Zodiac was in danger of looking for a ninth and tenth victim. The assumption therefore, was that victim number eight was probably killed sometime between the 'Dripping Pen' card on November 8th 1969 (or possibly November 9th), claiming seven victims and the Melvin Belli letter mailed on December 20th 1969. But again, taking the latter 'Bus Bomb' communication, Zodiac had claimed seven victims to end of October, not up to November 9th 1969. He did state seven victims on the 'Dripping Pen' card, but he added the extra hint that "you won't get the bad news for a while yet."
This may suggest that indeed, he had already killed again, prior to November 8th, but he simply wasn't announcing it to anybody, as the following communication would testify. We know that by the end of October (31st) the total was seven, therefore this unannounced eighth murder would had to have been committed from November 1st 1969 up to November 9th 1969. 
A contested piece of correspondence was the 'Fairfield' letter on December 16th 1969, claiming "I will go for government life." The accompanying drawing depicted the 'Bleeding Knife of Zodiac,' with eight drops of blood dripping from the weapon, suggestive of an eighth victim. Was this indicative of another Zodiac murder by knife, having been bolstered by his 'successful' attack, in theatric style, on Bryan Hartnell and Cecelia Shepard on September 27th 1969 at Lake Berryessa. Or was the knife just a reminder to his last crime we know he committed. If this correspondence was genuine, the term 'government life', may indicate any person in any state run organization, and a distinct hatred towards officialdom, which is unsurprising bearing in mind previous communications.
The question being, can anybody find the eighth murder spanning November 1st 1969 to November 9th 1969, in a relevant geographical location, that doesn't have the hallmarks of Zodiac. After all, he did state he would "change the way of collecting the slaves".  If this were the case, we simply wouldn't recognize it anyway.  

# A Salesian High School teacher, Daniel Williams had his house broken into, but nothing was taken. A man claiming to be the Zodiac Killer made several threatening phone calls beginning on October 23rd 1969, culminating with the caller saying "You're the dead duck" on November 2nd 1969. Later that day Williams took a drink from the refrigerator, but fortunately spat it out after noticing a metallic taste. The drink contained enough arsenic to kill. Would a teacher be considered 'government life'. The date fits the criteria and the death could have appeared like natural causes, or a killing of anger.
Daniel Williams residence was situated at 1234 Bush Street, Martinez, only 9 miles from the location of Zodiac's first crime at Lake Herman Road.
http://www.zodiacciphers.com/zodiac-news/youre-the-dead-duck

A few months ago, Alex Lewis secured a redacted document from the FBI regarding the sighting of an eight year old, in relation to the murder of taxicab driver Paul Stine on October 11th 1969. The document stated "Xenophon L Anthony, WMA, DOB 2/28/31, resides 3218 Jackson Street, San Francisco. For info ident division, San Francisco PD advised eight year old witness in murder of cab driver identified Anthony as possible subject in this matter."
Nobody can verify Xenophon Anthony as the Zodiac Killer, he may simply have been identified close to the crime scene or for that matter misidentified by the eight year old. But hypothetically, let us assume the eight year old was correct, and observed Xenophon Anthony in the proximity of the taxicab that fateful night.
The only way a child observing from the window of a residence can actually recognize somebody they knew, particularly at 9.58 pm at night, in less than ideal light conditions, is if they were viewing the unfolding events from a relatively close distance from the taxicab. In other words a residence close by. The closest residence to the crime scene was 3898 Washington Street, actually overlooking the taxicab, situated less than 30 feet away, the perfect vantage point to correctly identity a subject, known to the observer. The residence is also the most likely to be disturbed by a taxicab pulling up sharply, a muffled gunshot or any form of commotion on the street. The three teenagers across the street, by whatever means, had their attention drawn to the unfolding drama, therefore it is perfectly logical, that they may not have been the only ones.
Crucially, a simple records check placed an 8 year and 2 months old boy resident at 3898 Washington Street on October 11th 1969. This, although not conclusive, is likely the eight year old mentioned in the FBI document.      

Alex Lewis is not convinced the Zodiac Killer entered the Presidio Park with good reason, however the following will take the opposite stance and attempt to connect the killer's movements to 3218 Jackson Street, highlighted in the document on the right. In addition, reminding ourselves to the curious statements on the initial wanted poster.  
Whether or not Donald Fouke stopped the Zodiac is not important here, but the 'meeting' took place just shy of the Jackson and Maple intersection.
Witnesses in Spruce Street, detailed in the San Francisco Chronicle on October 12th 1969, reported seeing a man running into Julius Khan playground. The description was so similar to the ones given by Donald Fouke and the three teenagers, it seems inconceivable that this was not the same person that left the taxicab moments earlier. The only way it can be argued that this man entering the park wasn't the killer, is if we dismiss the testimonies of the witnesses in Spruce Street, while choosing to believe Donald Fouke and the three teenagers. The descriptions of the murderer given at all three points in the journey, not only overlap closely, but are testimony to the exact direction taken by the killer. Firstly, 3898 Washington Street, secondly, Jackson Street and thirdly, Julius Khan playground. To dispel this final sighting, is to dispel them all. 
This is where the Zodiac Killer takes over in his November 9th 1969 'Bus Bomb' letter. He charts his position throughout his entire journey, from the taxicab to the moment he left the park, almost like he was fitted with a GPS.
It is important to note that sniffer dogs were assembled on the outskirts of the park at certain points. The area of Arguello Boulevard and the Julius Khan playground were two notable areas, to sweep west to east, and south to north, covering the entirety of the park. (see here). The route Zodiac took will be told in his own words.
1. "2 cops pulled a goof abot 3 min after I left the cab. I was walking down the hill to the park when this cop car pulled up."
Donald Fouke corroborated this, stating he passed a WMA just past the intersection of Jackson and Maple, at a point exactly 3 minutes walking distance from the taxicab.
2. "I said yes there was this man who was runnig by waveing a gun & the cops peeled rubber + went around the corner as I directed them + I disappeared into the park a block + a half away never to be seen again."
One and a half blocks from the location of where Donald Fouke passed him, is Spruce Street. Zodiac stated he entered the park here, and several eyewitnesses agreed with him, even giving a near perfect description of him.        

3. "Hey blue pig I was in the park -- you were useing fire trucks to mask the sound of your cruzeing prowl cars. The dogs never came with in 2 blocks of me + they were to the west."
In view of the assembled sniffer dogs and activity along West Pacific Avenue, Zodiac had limited options, so headed east. The nearest dogs to Zodiac were the ones assembled by Julius Khan playground, so if they never came within two blocks of him, he must now have moved 2+ blocks east, by or just beyond Laurel Street.
You will notice Zodiac stated "there was only 2 groups of parking about 10 min apart." Here they were, two groups of police with sniffer dogs measured at 8 minutes separation by Google Maps.​
4. "then the motor cicles went by about 150 ft away going from south to north west." 

With the dogs fanning across the park, Zodiac gives us his final position before exiting the park, somewhere by the white cross. Zodiac having last been seen entering Julius Khan playground, motorcycles were traveling down West Pacific Avenue towards Presidio Boulevard and circling the park, searching for the killer.
This area provides plenty of coverage from the road and is approximately 150 feet away from any motorcycles passing by. He correctly states that the motorcycles would be travelling from south to northwest, along Presidio Boulevard.
But where does the killer go now.
The Zodiac Killer can head east, but it will be noticed that his directions and bragging have inadvertently taken us right by the residence of 3218 Jackson Street. A quick exit across West Pacific Avenue, through either Walnut Street or Presidio Avenue, to Jackson Street, places him only a couple of hundred feet from the doorstep, if indeed this was the killer's residence. Of course Xenophon Anthony may not be the killer, in which case, the 'Bus Bomb' letter author has, by sheer chance, taken us on a guided tour through the park directly adjacent to his residence.    
This takes us to our final thoughts, regarding the wanted poster released on October 13th 1969.
The poster bearing the name Chief of Police Thomas J Cahill stated "Suspect takes cab in downtown area at 9.30 pm and sits in front seat with driver. Tells driver destination is Washington and Laurel area or area near park or Presidio. Upon reaching destination, suspect orders driver to continue on at gunpoint into or near park where he perpetrates robbery."   

​Considering two people were present in the taxicab on October 11th 1969, one of whom is dead and the other not available for interview, where did this information originate from. It may have been supposition based on a recent spate of taxicab attacks in San Francisco, however the specific detailing of Laurel Street is noteworthy, in lieu of the absent trip sheet.
Assuming the killer had initially planned his murder on Washington Street and lived in the area, it would make sense to leave some form of 'buffer zone' from the site of the murder to his residence, a bare minimum of a block, preferably more, but all the time being wary of traveling any great distance on foot with the murder weapon and blooded shirt in tow. It's a delicate compromise.
It can be seen on the left and here on Google Maps that the intersection of Laurel and Washington Street is one block to Jackson Street, then one and a half blocks to 3218 Jackson Street, not too close, not too far, especially on foot, where time becomes more of a premium. It is actually a 5 minute journey. 
If the information on the wanted poster has any origin in fact, then Zodiac certainly did overshoot his destination, but this time it would have been four blocks. Understandable if he is in the process of threatening a nervous taxicab driver.
Either way the location of Washington Street, close to Presidio Park, would have provided the perfect contingency plan, to shelter from the police, if things didn't go to plan. Enter Donald Fouke and Eric Zelms.
If we believe the Zodiac and 'Bus Bomb' letter, and the eyewitnesses in Spruce Street, then the likelihood he had a car parked up, somewhere by Jackson and Maple Street, is not likely. Once Donald Fouke and Eric Zelms had faded into the distance, all he had to do was locate his vehicle and drive off. Instead he headed to Spruce Street and through the park. But did he head for 3218 Jackson Street. ​        

The Zodiac signed off the Bus Bomb Letter mailed on November 9th 1969 with the words "To prove that I am the Zodiac, ask the Vallejo cop about my electric gun sight which I used to start my collecting of slaves."  But to whom was the Zodiac referring. The answer could very well be Vallejo Police Chief Jack E Stiltz, a native Vallejoan who first joined the police force in 1939, and oversaw many changes, including the new station located at 111 Amador Street, before retiring with health issues in 1970. Jack E Stiltz died in 1974. 

The Zodiac sent three coded segments in three letters on July 31st 1969 to the San Francisco Examiner, San Francisco Chronicle and Vallejo-Times Herald, giving details of the first two crimes to prove he was the actual killer. The Zodiac Killer however was still questioned and Police Chief Jack E Stiltz still wanted more proof, as can be seen here in this extract from from the Saturday August 2nd 1969 San Francisco Chronicle. He requested the writer to send a second letter "with more facts to prove it."  

This story was featured again on Sunday August 3rd 1969 in the San Francisco Examiner (shown here on the left. Jack E Stiltz is 'still not convinced the letters and codes were written by the actual killer.' The police chief 'urged the writer to send more letters, with more facts to prove his connections to the crimes.'
The Zodiac Killer's response was swift when he mailed the 'Debut of Zodiac' Letter just one day later on August 4th 1969 to the San Francisco Examiner, to leave you in no doubt he was replying directly to Jack E Stiltz. The Zodiac's opening gambit was "In answer to your asking for more details about the good times I have had in Vallejo, I shall be very happy to supply even more material. By the way, are the police having a good time with the code? If not, tell them to cheer up; when they do crack it, they will have me." He went on to describe the Blue Rock Springs Park and Lake Herman Road attacks in much greater detail and effectively informed Jack E Stiltz about his replacement gun sight;  "What I did was tape a small pencel flash light to the barrel of my gun. If you notice, in the center of the beam of light if you aim it at a wall or ceiling you will see a black or darck spot in the center of the circle of light about 3 to 6 inches across. When taped to a gun barrel, the bullet will strike in the center of the black dot in the light. All I had to do was spray them as if it was a water hose; there was no need to use the gun sights. I was not happy to see that I did not get front page coverage."   
Fast forward to Presidio Heights on October 11th 1969 and police claims that Zodiac could not have been hiding in the park and had left fingerprints on the interior and exterior of the taxicab, particularly the blooded fingerprints on the driver side panel. Zodiac again felt compelled to reply in the November 9th 1969 Bus Bomb Letter, "I have grown rather angry with the police for their telling lies about me...... p.s. 2 cops pulled a goof abot 3 min after I left the cab. I was walking down the hill to the park when this cop car pulled up + one of them called me over + asked if I saw anyone acting suspicious or strange in the last 5 to 10 min + I said yes there was this man who was runnig by waveing a gun & the cops peeled rubber + went around the corner as I directed them + I disappeared into the park a block + a half away never to be seen again." and again asked for press coverage similar to the 'Debut of Zodiac' Letter,  "By the way it could be rather messy if you try to bluff me. PS. Be shure to print the part I marked out on page 3 or I shall do my thing. To prove that I am the Zodiac, Ask the Vallejo cop about my electric gun sight which I used to start my collecting of slaves."
The last time the Zodiac was doubted he supplied extra details of the Blue Rock Springs and Lake Herman Road attacks to Vallejo Police Chief Jack E Stiltz and he again did the same in the Bus Bomb Letter, reminding everybody that he indeed was the Zodiac Killer. In other words do not doubt him and "Ask the Vallejo cop about my electric gun sight which I used to start my collecting of slaves." The Vallejo cop he is referring to is Jack E Stiltz. The Vallejo cop, to which he sent details about his improvised gun sight in the 'Debut of Zodiac' Letter only three months earlier. He proved to Jack E Stiltz that he was both the letter writer and the killer, and again here in the Bus Bomb Letter, he is referring back to this Vallejo cop.., and to not doubt him again.  

"p.s. 2 cops pulled a goof abot 3 min after I left the cab. I was walking down the hill to the park when this cop car pulled up + one of them called me over + asked if I saw anyone acting suspicious or strange in the last 5 to 10 min + I said yes there was this man who was runnig by waveing a gun & the cops peeled rubber + went around the corner as I directed them + I disappeared into the park a block + a half away never to be seen again". Bus Bomb Letter 11/9/69.
It can be seen the Zodiac Killer is claiming an encounter with two policemen, only minutes after the murder of Paul Stine at Washington and Cherry Street.
In the 2007 documentary 'This is the Zodiac Speaking,' Armond Pelissetti is clearly lending credence to this encounter, when referring to Officer Donald Fouke, who supposedly spotted the Zodiac Killer by 3712 Jackson Street. Pelissetti said "I spoke to Officer Fouke later that evening and was unaware that he had stopped anybody, black, white or any other color, however in subsequent conversations with him, he told me that he did stop somebody". Donald Fouke denies that he stopped anybody. It is clear that the Zodiac Killer was not privy to this conversation, and the supposed stopping and questioning of a suspect was not featured in any newspaper articles prior to the November 9th 1969 'Bus Bomb' letter. The Zodiac claimed that the encounter occurred about 3 minutes after he left the taxicab. So let us examine the timeline of Donald Fouke and the Zodiac Killer that night.   

Armond Pelissetti stated in the documentary that he and Frank Peda responded 'red light and siren' after the dispatchers call at 9.58 pm.
So let us surmise for now the Zodiac left the scene at 9.56 pm. After three minutes walking the Zodiac would have arrived close to the intersection of Jackson and Maple, by 3712 Jackson Street, at 9.59 pm, supposedly where this encounter happened.
Donald Fouke stated that he saw a white male entering the stairwell to 3712 Jackson Street. Donald Fouke also received the dispatcher's call at 9.58 pm, while he and his rookie partner Eric Zelms were traveling northbound on Presidio Avenue, having just passed Washington Street. The journey time from this location is approximately 1 minute to 3712 Jackson Street,.meaning Donald Fouke would have arrived at 9.59 pm- the exact time the Zodiac would have been passing this location.
So Zodiac's claim of this encounter holds up to the timeline, and bearing in mind Armond Pelissetti's claim that Fouke stated to him that he stopped somebody, it appears to corroborate Zodiac's claim that "two cops pulled a goof". 
Again, the Zodiac Killer was not privy to the police officers claims or statements prior to November 9th 1969, so it was either a lucky guess on his part or he was telling the truth. 
It is easy for the police and newspapers to discredit  the Zodiac Killer, simply by saying 'they are the claims of a madman' or 'psychopath'. They claim in no way did the Zodiac speak to the police officers that night, nor did he likely enter the park on account of the sniffer dogs employed in the search. But this may simply not be the case.
His claim above, of talking to Donald Fouke and Eric Zelms is likely true, as the timeline suggests, and unless Armond Pelissetti was lying, and I see no reason why he should, it placed Donald Fouke in a direct path with the killer at 9.59 pm that night- not withstanding the fact Zodiac knew of Donald Fouke's route that night, that ties in perfectly. The embarrassment of questioning a suspect and then letting him on his way, may have been something that would be better glossed over, and certainly something the Zodiac was keen to capitalize on in his extensive 'Bus Bomb' letter, insisting it must be printed in the newspapers. In other words he wanted to highlight this fact- something that had clearly been kept under wraps. But if this were the truth, how many other of the Zodiac claims were true. Let's take a look. 

"the cops peeled rubber + went around the corner as I directed them + I disappeared into the park a block + a half away never to be seen again," The encounter was claimed to have occurred at 3712 Jackson Street, just before the intersection of Jackson and Maple. So, if the Zodiac disappeared into the park one block and a half away, we shall travel this distance.
Although just under a block and a half, the nearest to this description is Spruce Street, shown here. Here the Zodiac Killer could easily enter the park at a safer distance from any searches that may have materialized from where he was initially seen. It also lies closer to his initial claim of a murder by "Washington and Maple", if this was his original intended destination.
Of course, some of his claims to have been hiding in the park could have been bolstered by adding detail he subsequently read in the newspapers, but there is one thing he stated that not only boosts the idea he entered the park via Spruce Street and hid in the trees there, but is descriptive enough to provide us with a location.
This is what the Zodiac said in the Bus Bomb Letter "I gave the cops som bussy work to do to keep them happy. I enjoy needling the blue pigs. Hey blue pig I was in the park -- you were useing fire trucks to mask the sound of your cruzeing prowl cars. The dogs never came with in 2 blocks of me + they were to the west + there was only 2 groups of parking about 10 min apart then the motor cicles went by about 150 ft away going from south to north west."  
The Zodiac again backs up the idea he entered the park via Spruce Street saying "The dogs never came with in 2 blocks of me + they were to the west." This suggests that if we travel just over two blocks west of the Spruce Street entrance to the park, this is where he was observing the police, fire trucks, motorcycles and dogs from. See here. The Arguello Boulevard entrance to the park is just over two blocks. 

We now possibly have Zodiac entering the park here, but can we narrow it down further. In the topographic maps of 1968, the layout of the park's trees and hedges have altered little to affect this analysis and can be viewed here. Many of the police would have flooded the park via the Arguello Boulevard entrance- this is the area of dense growth highlighted on the map by the red ellipse shown to the left. This activity was noted by the killer "Hey blue pig I was in the park -- you were useing fire trucks to mask the sound of your cruzeing prowl cars. The dogs never came with in 2 blocks of me + they were to the west." But he went on to say one further critical statement, that may have pinpointed his exact location within the park, "there was only 2 groups of parking about 10 min apart then the motor cicles went by about 150 ft away going from south to north west." 
They were going from south to north west.
So what road was the Zodiac describing from his vantage point, allowing him to view this directional movement of traffic.
There was elevation in the park- but his view would also have been masked by trees. This image on Google Maps shows part of the Arguello Boulevard masked by trees, however, a little further on it opens up. This section of Arguello Boulevard frees itself from the tree line and heads from south to north west, just as the Zodiac stated in the 'Bus Bomb' letter. So all that is left for us to do is pinpoint his location, allowing him to clearly view this area. The police would certainly have focused on this area, as it was not only a key entrance to the park but also an area of dense growth, availing many possibilities to escape into. So let us travel back to the entrance to the park from Spruce Street.
Knowing of the commotion to the west, logically the Zodiac should have accessed cover immediately to the east after entering the park- somewhere in the region shown below. Notice the line of sight available to the Zodiac to that portion of Arguello Boulevard we mentioned earlier, running from south to northwest, thereby giving us an exact position of the Zodiac Killer on October 11th 1969 in the park, as we may likely ever have.
It may well be the case that if the Zodiac didn't have a car waiting somewhere by the intersection of Jackson and Maple, for fear of vehicle identification, and if so, then his claim of entering the park that night, might well be true after all.
After viewing the police to the west, including any scent dogs, he may have cut his losses. He couldn't head west, and he surely wouldn't have re-entered West Pacific Avenue or Jackson Street, so the sensible option available to him, was to head eastwards toward Cow Hollow or the Marina District. But bearing in mind he may have been covered in blood, is it possible he lived in a house backing onto the park or likely had his vehicle parked here, affording him a distinct separation from the Presidio Heights area. Or was the Zodiac Killer a liar as Chief of Inspectors Martin Lee contended, and the Zodiac Killer was never in the park at all.

An article in the San Francisco Chronicle by Paul Avery dated November 12th 1969 and titled "I've Killed Seven, The Zodiac Claims", clearly states 'As proof the letters were from the true Zodiac and not an imposter, the mass murderer enclosed another portion of the piece of shirt he tore off the body of San Francisco taxi driver Paul Stine'. Then in a second article on December 28th 1969 entitled "New Zodiac Letter...Fears He'll Kill Again", it states 'A few days after the Stine killing, Zodiac sent a letter to San Francisco newspapers and also included a swatch of Paul Stine's shirt. Another letter and another piece of Stine's shirt was sent to a Newspaper on November 11th'. See here. The 340 Cipher and Dripping Pen Card/Bus Bomb Letter were mailed in close succession on November 8th and 9th at the weekend and may have arrived at the beginning of the following week, accounting for the November 11th attribution. Then a Youtube documentary commencing at the 3 minute mark confirms that a total of three shirt pieces were sent. Two articles and one documentary, all indicating that a third section of Paul Stine's was sent accompanying either the 340 Cipher or Bus Bomb Letter.
Had the Zodiac Killer set aside three portions of shirt to send, it is highly unlikely he would want to be sitting on incriminating evidence for too long and after the murder of Paul Stine in Presidio Heights on October 11th 1969 he would mail his three portions of shirt with his next three correspondences. His first being the October 13th letter, just two days after the murder, his next letters were postmarked within one day of each other, so he sent the second portion with these and the final piece was mailed with the Melvin Belli Letter on December 20th 1969. What he didn't do however, was mail a piece of shirt with the Fairfield Letter on December 16th, four days before the Melvin Belli Letter, why, because it was a fake Zodiac letter, not mailed by the killer. This is not conclusive, but other features of the Fairfield Letter, suggest this correspondence was mailed by an impostor, who knew little about the mind of the real serial killer. 

It cannot be known for certain, but the Fairfield Letter seems to be suggesting a link to the Lake Berryessa stabbing on September 27th 1969, the only crime committed thus far with a knife. It was always questioned why the Zodiac failed to brag about his theatrical crime on the shoreline of Lake Berryessa, after all, it was his most daring to date. There is no definitive answer, but one thing the Zodiac Killer never foresaw, was that he was to leave a surviving witness, in Bryan Hartnell. He could have bragged endlessly about this crime, but in hindsight his failure to kill both victims actually played right into his hands. The detailed account of Bryan Hartnell, the description of the killer's costume and the extensive newspaper accounts, gave him all the publicity he could ever have wished for. What more was there to add. However, newspaper accounts were starved of the full details, in that the 'by knife' writing on the car door of Bryan Hartnell's car was withheld, probably to flush out the real killer from any subsequent hoaxers, and the Fairfield Letter may be one example.
Anybody who was aware of the Lake Berryessa attack could have concocted the phrase 'The Bleeding Knife of Zodiac', and more importantly its failure to highlight 'by knife' was an opportunity missed from a killer now determined to link himself to the authenticity of his correspondence, by enclosing the swatches of Paul Stine's shirt. The Zodiac Killer had his ego dented when his first cipher was cracked in a matter of days by schoolteacher Donald Gene Harden and his wife, Bettye June Harden, two amateur sleuths. His response was to send us the still unsolved 340 Cipher, crafted either with no solution or a solution that went far beyond simple homophonic substitution. The Fairfield Letter however, is a retrograde step into mediocrity, when the supposed Zodiac Killer now reverts back to scribbling nine symbols, showing little effort, in the apparent guise of a small code and beginning his letter with "I just want to tell you this state is in trouble, I will go for the government life", more reminiscent of a political agenda, with bold claims of another potential 38 victims. The 'knife' wording does look similar to the writing on the card door at Lake Berryessa, but the template for these letters was freely available throughout his correspondence up to this point. But he fails to corroborate this letter with a swatch of Paul Stine's shirt, why, because the real Zodiac Killer was to contact authorities just four days later.   

The Fairfield Letter was mailed on December 16th 1969, sandwiched between the Bus Bomb letter of November 9th and the Melvin Belli letter on December 20th and it was this reason, along with its design that has placed this relatively early letter into the section of unlikely Zodiac correspondence. The main reason for this centers on the belief that the Zodiac Killer, after murdering Paul Stine in Presidio Heights on October 11th 1969, actually mailed three pieces of Paul Stine's shirt to the newspapers, not two as is widely believed. This is not a new concept and there is a thorough section devoted to this on the excellent ZodiacKillerSite forum here, but for those who have not come across this, we shall do a brief summary, before bringing the Fairfield Letter into the equation.
It is widely acknowledged that two pieces of Paul Stine's shirt were sent, firstly to the San Francisco Chronicle on October 13th 1969, just two days after his murder and secondly on December 20th 1969 to the home residence of prominent attorney Melvin Belli, but it was likely a third piece was sent along with the '340 Cipher and Dripping Pen Card' on November 8th 1969 or Bus Bomb Letter a day later, outlined in two articles written by the San Francisco Chronicle and mentioned in a Youtube documentary. Anyone can believe in mistakes, but the wording in the Chronicle is specific, to say the least and the mailing of three portions of Paul Stine's shirt makes perfect sense, from photographs of the shirt on the Zodiac Killer Facts site marked A, B and C. 
Here is an excerpt from the FBI files (Zodiac 5 page 46/249), clearly showing three shirt pieces were mailed.  
       

The My Name is....Cipher was sent to the San Francisco Chronicle on April 20th 1970, containing a short 13 symbol code, particularly remembered for the positioning of three circled 8's within its design. They may have been astrological symbols, but for the purpose of this article, it will be shown numerically how the possibility exists, that indeed the Zodiac was using the 888 numerology as a key ingredient through his first three murders, his first three attack sites, before cryptically ending with his correspondences, after the brutal murder of Paul Stine in Presidio Heights on October 11th 1969 and the 340 Cipher one month later. 
As usual, this is not a claim to the solution, just an idea that could possibly be added to by contributors or simply discarded as unlikely. Some, but not all, of the following has been covered in previous posts.
From the start of his murderous campaign on December 20th 1968, until the 13 Hole Postcard on October 5th 1970, twelve out of the thirteen victims closely associated with the Zodiac case had either disappeared or been murdered on the first day of the 13 Moon Calendar week. To view how this calendar works visit here for a brief explanation.
Below is the list compiled previously, along with the Zodiac's confirmed four attacks.   

It can be seen that his first three attacks at Lake Herman Road, Blue Rock Springs Park and Lake Berryessa, all fall on the first day of the week on the 13 Moon Calendar and all on the 8th day of the month, to produce the 888 numerology, but obviously, this means little on its own, so we shall continue.
It was then shown that one of the most noticeable features that resided on the 340 Cipher, was the near use of the name Zodiac on the final line and it was conjectured that this may have been a clue to his third cipher, when the My Name is....Letter arrived five months later on April 20th 1970, thereby continuing the theme of numerology.
Since the Zodiac Killer exhibited all the traits of an egotist, it would not have been unusual for him to use his own moniker as a Key and by placing this key alongside the apparent use of his name on the 340 Cipher, we may find an answer. So by using simple mathematics and no massive leaps of faith, we shall count numerically the difference between the respective six columns. The first three letters produce three 0's and the second three letters produce three 8's. Now circle the three 8's with the three 0's, to construct the feature found within his next cipher. Also note the positioning of the Zodiac crosshair and the upside down Aries symbol in relation to both ciphers. SEE DIAGRAM BELOW.

Paul Stine, on October 11th 1969, was to become the final confirmed murder by the Zodiac Killer. Two days later, he mailed a swatch of Paul Stine's shirt to the San Francisco and declared ' I am the murderer of the taxi driver over by Washington St and Maple St ' and culminated this, one month later with his 340 Cipher on November 8th 1969. But what did the 340 message hold.
Was it possible he opened up with the first line from Genesis ' In the beginning god' and ended it with a signature from Jesus, or the Zodiac, beholding the 888 hidden within its encryption and signifying that his search for the perfect afterlife was just getting started.   

The ecliptic passes through 12 constellations to form our Zodiac, used in horoscopes to predict the future. The Zodiac Killer sent us the 'Bus Bomb' letter, to which he displayed a crosshair at the foot of his correspondence, marked with five crosses and dotted sections to separate the circle into 12 equal divisions of 30 degrees. There was a possibility this was to become his compass or template to his crimes, the ones he had already placed X's next to and the remainder, as he stated at the top of the 'Bus Bomb' letter on November 9th, that would not be announced. He wrote ' up to the end of Oct I have killed 7 people. I have grown rather angry with the police for their telling lies about me. So I shall change the way the collecting of slaves. I shall no longer announce to anyone. When I committ my murders', but he was to leave us a clue. Image of the 'Bus Bomb' crosshair with X's.  

But what we shall examine here is the statement the Zodiac wrote on the 340 Cipher and 'Dripping Pen' card, namely "This is the Zodiac speaking.  I though you would need a good laugh before you hear the bad news. You won't get the news for a while yet", implying his evil deeds were not far away. His next confirmed contact after this, was the Melvin Belli Letter claiming a search for a ninth and tenth victim and by inference No 8 has already been committed.
A 10th victim is confirmed by the arrival of the 'My Name is Cipher' on April 20th 1970. This correspondence could have read Zodiac 12 SFPD 0, if he had been successful in the murder of Kathleen Johns and her infant daughter, one month earlier on March 22nd 1970, commonly referred to as the 'Modesto Attack'. This crime may not have been the work of Zodiac, but he claimed it was, and if indeed it was, it was to be a failed murder attempt he was not about to forget.
The Zodiac Killer's three early crimes were in static locations, that is, he did not coerce or force his victims to a predetermined location. It has been suggested by some Zodiac researchers that the Paul Stine murder was chosen because of his ability to manufacture an exact grid position to fit his location point on the 'Bus Bomb' letter crosshair. The next two incidents strongly linked to the Zodiac Killer were the Modesto abduction of Kathleen Johns on March 22nd 1970, followed by the Donna Lass disappearance on September 6th 1970, with one or both employing the use of a car to abduct the victim, with the intention of possibly seeking out his predetermined grid location. But there is another reason that may link both Kathleen Johns and Donna Lass.
The Zodiac Killer could quite easily have shot Kathleen Johns through the driver side window of her vehicle, as he had done at Blue Rock Springs Park, but chose to subject his victim to what appeared an aimless drive around the countryside of Tracy, CA, after which she escaped to a nearby field. If this was a Zodiac crime,  was the Bay Area murderer possibly aiming for somewhere in the region of Antioch, CA, which falls directly on the north-east line on the map above, and conveniently on the way back to the Vallejo area, where it has been widely speculated that he resided. 
Kathleen Johns may have denied the Zodiac Killer his 11th and 12th victim this time, but was he to remind us of it exactly one year later on March 22nd 1971, when the disputed 'Pines' card landed at the door of the San Francisco Chronicle. The reason behind its design is not certain, but what was apparent, was that the largest writing on the 'Pines' card was "Sought Victim 12", a clear indication in the past tense, he had indeed sought his 12th victim, but failed. This card signifying 12 was out of sequence with the the other cards, because it came after the 'Little List' letter on July 26th 1970 claiming a victim count of 13, the '13 Hole' postcard on October 5th 1970 also claiming 13, the 'Halloween' card on October 27th 1970 inferring a 14th victim and the 'Los Angeles' letter on March 13th 1971 claiming 17+ victims.

The Zodiac Killer sent the 'Pines' card 6 months after the disappearance of Donna Lass. The significant delay may have been orchestrated to tie in with the anniversary of the Modesto attack, emblematic of the fact he was unable to place Kathleen Johns on the north east grid line (shown above) as intended on the 'Bus Bomb' map, so he found a replacement on the exact same grid line, that of Donna Lass at South Lake Tahoe and inextricably linked them both by the number 12 and March 22nd.

After the brutal attack on Bryan Hartnell and Cecelia Shepard at Lake Berryessa on September 27th 1969, the perpetrator left his calling card on the car door of Bryan Hartnell's Karmann Ghia, as a form of confession to his crimes, listing the Lake Herman Road double murder of Betty Lou Jensen and David Faraday on December 20th 1968, the Blue Rock Springs Attack on Michael Mageau and Darlene Ferrin on July 4th 1969 and the latest attack, that ended the life of Cecelia Shepard.
Forty two days later he mailed the now infamous Dripping Pen Card, containing the still unsolved 340 Cipher. Inside he wrote some key words "I get awfully lonely when I am ignored, so lonely I could do my thing", placing reference to several months, December, July, August, September and October at the bottom of the correspondence, finishing with the number 7, presumably his murders so far, as opposed to his victims.

​Let us examine the claim of seven murders on the Dripping Pen Card once more, comparing it to the Bus Bomb Letter, mailed just one day later. At the foot of this correspondence he gave us a diagram of a crosshair, with five X's on its circumference.
If the Zodiac  crosshairs on the left  are placed over a map (see below), with the center of the circle placed over Mount Diablo and rotated, we find that despite its crude manufacture, that three of the X's can be drawn through from the center point to align approximately with his first crimes in Benicia and Vallejo, as well as the Presidio Heights murder of Paul Stine and the Lake Berryessa attack. 
If this was the reason for its design, then by elimination we are left with two X's unaccounted for. This would suggest that the 6th and 7th victims he claimed in the Dripping Pen Card were in fact true, however not a double murder at all, but two individual crimes.
If we return to the commonly held assumption, that we are looking for two murders in August, taking the Bus Bomb overlay at face value, then all we have to do is follow the two lines on the right of the diagram below and search for similar murders in August 1969 at locations where each line passes over, or in close proximity to, that have the hallmarks of the Zodiac Killer.
But be warned, if you believe the Zodiac Killer "you deserve to have holes in your heads."