The Zodiac Killer mailed the 'Button' letter and Phillips 66 Map on June 26th 1970 overlaying his crosshairs over Mount Diablo. Just a month later, realizing the clues in the Button letter were insufficient, he gave us the answer in the 'Little List' letter declaring "PS. The Mt. Diablo Code concerns Radians & # inches along the radians". The crosshairs with the bold SFPD = 0 were telling us exactly where he planned to 'set his bomb'. By identifying the location in degrees, using a black, bold circle and coupling it with a 'dig' at the San Francisco Police Department, he was effectively giving us the target and the location. His target was the San Francisco Police Department subtended at an angle of 246 degrees from true north. Bearing in mind his bomb threats were focused in San Francisco, all we had to do was find the police department. How experienced the Zodiac Killer was regarding radians is unknown, but he designed a form of clock face with a directional marker pointing true north and then stated "0 is to be set to Mag.N" (which was approximately 17 degrees in 1970). We don't actually need to know how many radians he intended, from which point, and whether they were meant to travel clockwise or anticlockwise around the clock face, because the bold, dark circle is already the answer.   

On the left I have combined the crosshairs from the 'Button' and 'Little List' letters. The bold, dark circle is 246 degrees around the circumference (which is 4 radians + magnetic north). A radian is 57.3 degrees, so 4 X 57.3 + 17 degrees = 246 degrees. If we deduct 2 radians from true north we get 360 - 114.6 = 245.4 degrees. So, whether we use 2 radians anticlockwise from true north or 4 radians clockwise from magnetic north, the result falls within the circumference of his bold, dark circle (246 and 245.4 degrees). 

Drawing a line through this bold, dark circle from Mount Diablo and across San Francisco, it passes near only one police station, that of Ingleside. It isn't absolutely accurate, but it is the closest police station the measurement relates to. This is why he added SFPD next to the bold, dark circle rather than placing it at the foot of his letter in customary fashion. His bomb was to be set in the vicinity of the San Francisco Police Department at Ingleside. Whether he actually meant it is debatable, but it was the threat that was likely his main goal - sowing more fear into the heart of San Francisco.

The Zodiac Killer made many bomb threats in the 1970s, including references to "black power" in the April 28th 1970 'Dragon' card, along with his Symbionese Liberation Army letter in 1974. This has led some to ponder if the Zodiac Killer was somehow affiliated to a radical group, or possibly infuriated by groups such as the Black Liberation Army or Black Panthers, stealing the limelight away from his dwindling publicity: "I would like to see some nice Zodiac buttons wandering about town. Everyone else has these buttons like, black power, melvin eats bluber, etc". The Zodiac Killer may have been mailing correspondence well into 1971, with communications such as the July 13th 1971 'Monticello' card, 148 character cipher, and quite possibly, the unseen DMV letter. At this period of time, it appeared as though the Zodiac Killer was desperately attempting to connect himself to the murders of Debra Gaye Furlong, Kathy Ann Snoozy and Kathy Bilek, all savagely stabbed in excess of fifty times.   

Mary Alice Willey arrived in San Francisco in 1969, making some questionable alliances, including the black power movement. "She became a strident devotee of George Jackson, the charismatic but militant San Quentin inmate who had gained international fame for his best-selling prison classic, "Soledad Brother." She wrote letters to Black Panther Johnny Spain, who was also incarcerated at San Quentin. And she began associating with members of the Black Liberation Army, a violent offshoot of the Black Panthers that would become implicated in the Aug. 29, 1971, killing of a police officer at San Francisco's Ingleside Station. There is reason to believe that Mary Alice may have played a role in the attack and the slaying of Sgt. John V. Young". Read more at the San Francisco Chronicle. 

While in San Francisco she dated a fellow student, Patrick Warren McDowell, who claimed he belonged to the Symbionese Liberation Army, a group ultimately responsible for the kidnapping of Patty Hearst in 1974. In February 1971 he was arrested for the failed robbery of the Sugar Bowl Ski Lodge near Lake Tahoe, having borrowed Mary Alice Willey's car.

If the Zodiac Killer was still closely following the news in 1971, as it appears he was, regarding Snoozy, Furlong and Bilek, then it wouldn't have gone unnoticed that the Ingleside Police Station he had threatened to bomb just over a year ago, had now come under attack. On August 21st 1971 a gun was smuggled to George Jackson in San Quentin Prison. As Jackson was being escorted back to his jail cell, a guard noticed the gun. Jackson raised the weapon and, paraphrasing Vietnamese revolutionary leader Ho Chi Minh, declared: "This is it, gentlemen. The dragon has come." As he later ran across the prison courtyard, a guard opened fire killing Jackson instantly. 

On August 29th 1971, a woman who bore a resemblance to Mary Ann Willey, wearing a blond wig, entered Ingleside Police Station to report a stolen purse. "Police have long thought the woman who had come to the station to report her stolen purse was a lookout connected to the Black Liberation Army, and they believed that woman was Mary Alice". Chronicle.  A short time later several black men entered the station and murdered John V. Young with a shotgun through the grill of the reception desk. Within two weeks of this attack Mary Alice Willey had vanished. 

On September 11th 1971 a worker stumbled across the body of a woman while driving along the Delta-Mendota Canal in Stanislaus County near Patterson - close to the abduction site of Kathleen Johns on March 22nd 1970. There was no evidence of sexual assault, but she had been stabbed at least 65 times, and her murderer had attempted to sever her fingers and hands. An identification was not made. 

"In March 1970, a pregnant woman and her 10-month-old daughter were abducted near Modesto by a man who drove them around the valley and, according to some police reports, threatened to kill them. Kathleen Johns and her daughter ultimately escaped and hitched a ride to the police station in Patterson. While giving her statement, Johns reportedly saw a drawing of the Zodiac Killer and claimed he was the one who abducted them.

Johns' conflicting statements, though, cast doubt upon whether she had, indeed, encountered and survived the Zodiac. The murder Hedrick is revisiting happened just 18 months after that abduction. The Zodiac claimed 37 kills, though only the five were confirmed. There's nothing to suggest the Zodiac Killer, who never was captured, claimed credit for this murder, sheriff's Detective Marc Nuno said". Read more at The Modesto Bee.

Nearly four decades later, in September 2008, her body was exhumed from Patterson cemetery, and using a forensic sculptor to reconstruct her face and modern DNA testing, she was finally identified as Mary Alice Willey.​

The Zodiac Killer gave us a map code on June 26th 1970, stating the "map coupled with this code will tell you where the bomb is set". To this day no bomb has been unearthed and the threat was likely an idle one, designed primarily to create fear within the American community. However, the map and code were real, and the answer to both has probably been sitting in plain sight for nearly fifty years. The Zodiac, aware that the 32-Symbol cipher was unable to be broken because it had 29 different characters, gave us all the answers one month later when he mailed the July 26th 1970 Little List letter.

The numerous suggested bomb threats were all mailed to the San Francisco Chronicle, so it was evident that his threats were focused on San Francisco itself - which is why the Mount Diablo map included San Francisco and Vicinity rather than just the area around Mount Diablo. The Little List letter was replete with all the information required to crack his map code. In the Button letter (June 26th 1970) the author gave us the "map coupled with this code will tell you where the bomb is set," and just one month later, clearly told us that the code "concerns Radians & # inches along the radians". Therefore, the code will at least contain the words "radians" and "inches" in the answer. In fact, it tells us exactly where the intended bomb was to be set, within the design of the crosshairs with the bold black circle. With the threats geared towards schoolchildren and police, it is apparent that these were the likely targets. The reference to SFPD=0 being incorporated within the crosshairs, along with an accentuated black, bold circle suggesting a location, should be the biggest clue of all. His intended target was the San Francisco Police Department - the location of which can be found within this bold circle. 

The Zodiac Killer referenced "radians" and "inches" (not parts of radians and inches), so with probably just the use of a ruler back in 1970, the Zodiac Killer would measure his intended target this way. Therefore, if he is one eighth of an inch off in his measurements we can forgive him this textual indiscretion. Fortunately, we have Google maps, so the task is much easier.
With an intended target in San Francisco, there is only one answer possible to the "radians" and "inches" conundrum, and it's governed by geography. 1 radian = 57.3 degrees, 2 radians = 114.6 degrees, 3 radians = 171.9 degrees, 4 radians = 229.2 degrees and 5 radians = 286.5 degrees. This is detailed crudely on the map below.

It is apparent that Zodiac wasn't referring to 5 radians, as a line subtended from Mount Diablo at this angle would pass north of San Francisco. The same applies to 3 radians which runs parallel to San Francisco. Therefore, the answer has to be 4 radians or 229.2 degrees. The lines drawn below are only approximations, so are not pinpoint. 4 radians or 229.2 degrees passes over San Francisco somewhere in the vicinity of the airport - but this isn't the answer. If we add back the magnetic north value of 17 degrees in 1970, it equals 246.2 degrees. After all, Zodiac stated on the map, it was "to be set to Mag.N". How do we know 246.2 degrees is the correct angle to be subtended from Mount Diablo? The answer is simple - Zodiac told us so. Place the crosshairs above over a compass rose. A line subtended from the center of the compass rose passes exactly through the center of the bold black circle. In other words, the bold black circle is positioned at 246.2 degrees around the crosshairs. This is 4 radians + 17 degrees (magnetic north). Now all we have to do is find the inches subtended along the 246.2 degree line. This is even easier.     

The map scale is 6.4 miles to the inch, so the geography of San Francisco is self-constraining.
It is approximately 26.5 miles to the eastern edge of San Francisco from Mount Diablo (using the angle of 246.2 degrees).
4 inches would equal 25.6 miles, therefore, 4 inches subtended from Mount Diablo would land in the sea. Unless the Zodiac Killer had a submarine to bury his bomb, this is not very likely.
It is approximately 34 miles to the western edge of San Francisco from Mount Diablo (using the angle of 246.2 degrees). 
6 inches would equal 38.4 miles and again would land in the sea.

Therefore, the answer has to be five inches along the 4th radian (plus magnetic north of 17 degrees). If this lands over the San Francisco Police Department we are in business. But first, we shall fill in the 32-Symbol code using the words or clue given by the Zodiac Killer in the July 26th 1970 Little List letter. The section below is almost the complete solution to the 32-Symbol code. Note how the Zodiac Killer inserts a hashtag style character between the "&" and "inches", with an arrow pointing between these two pieces of text. He is telling us to insert something here. We know from the above calculation it must be five inches, thereby completing the phrase: "P.S The Mt.Diablo code concerns Radians & 5 inches along the radians".
​

Richard Radetich, the fallen officer, possibly referred to in the Zodiac Killer's Button letter was initially assigned to Ingleside Police Station, before moving to Park Station and eventually to Accident Investigation.

Footnote: What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his Little List crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.​ The following article shows where the exact location of the bomb was to be set, on the embankment of the Southern Freeway, just 274 feet from Ingleside Police Station. The Answer to the Mount Diablo Code.

In analyzing the Button letter map and code, mailed on June 26th 1970, it is imperative we take a close look at the Zodiac Killer correspondence in the preceding few months to this communication for any clues to his mindset and intentions. There will be no definitive solution to the 32-Symbol code presented here, although a location for where his bomb was "to be set" can be argued with confidence, using four pieces of Zodiac material.

On April 20th 1970, the killer mailed 'The My Name is..Cipher' and stated "I hope you do not think that I was the one who wiped out that blue meannie with a bomb at the cop station.  Even though I talked about killing school children with one. It just wouldn't doo to move in on someone else's teritory.  But there is more glory in killing a cop than a cid because a cop can shoot back". The Zodiac Killer was referring to the murder of San Francisco police officer Brian McDonnell on February 16th 1970, two months earlier, when a bomb exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood.

He would back up this correspondence with the Dragon Card just one week later on April 28th 1970, declaring "I hope you enjoy yourselves when I have my blast". This card featured elements of the book Don Quixote, a novel by Miguel de Cervantes Saavedra, in which Alonso Quijana, a prolific reader of books, became so mesmerized by the chivalry contained within them, that under the assumed name of Don Quixote, along with his squire Sancho Panza, began a quest to revive this virtue. What the Zodiac Killer was inferring with this particular card can be debated, but the 1899 Waller Street Police Station is situated on the boundary of the San Francisco Golden Gate Park and in close proximity, also situated in the park, is the memorial statue of Miguel de Cervantes, featuring Don Quixote and Sancho Panza. Was the Zodiac Killer insinuating an attack close to the police station and park, similar to the murder of police officer Brian McDonnell? 

Then, on June 26th 1970, this communication arrived, insinuating the murder of another police officer, Richard Radetich (25). On June 19th at 5:25 am he was gunned down by three shots from a .38 caliber revolver at point blank range through the driver side window of his vehicle while in the process of serving a parking ticket by 643 Waller Street, San Francisco, in the Lower Haight District and subsequently died 15 hours later. The murder of Richard Radetich, as of writing, remains unsolved.

​The Zodiac Killer appeared to be heavily centering his focus in the Haight District. The statue in the park, 1899 Waller Street and 643 Waller Street all fall within a 2 mile radius, featured through three consecutive mailings. It is therefore this locality of San Francisco we shall again turn our attention to, when considering where the Zodiac Killer may be directing his threat towards in the Button letter, using recent history to predict the future.

There is good reason to believe the Zodiac Killer was threatening an attack on Ingleside Station-San Francisco Police Department, located at 1 Sgt John V Young Lane, named in honor of Sgt. John Young, killed by gunmen in 1971 after they stormed the police station. Ingleside Station is 4.6 miles south of 1899 Waller Street. The Zodiac Killer never followed through on many of his claims, but this may very well be the location he was threatening to bomb on June 26th 1970. So here is the evidence.

When the Zodiac Killer mailed the Button letter, it was accompanied by a Phillips 66 road map and his crosshairs, stating they were "to be set to Mag.N." That is magnetic north, calculated at 17 degrees in 1970. Clearly, he soon realized that the information or code he supplied, coupled with the Phillips 66 map, was insufficient to crack the cipher or determine a location for the bomb. One month later, he rectified the problem with the Little List letter mailed on July 26th 1970, when he incorporated two further crosshairs, with all the clues we needed.     

This was the first crosshair (see right).

The Zodiac Killer continually taunted police with his running victim total, always attributing the police with zero. This was nothing new. However here he deliberately brings attention to the zero, marking it noticeably darker, as though it has increased significance. It is also placed within the crosshairs, indicating an area within his sights. Bearing in mind the acronym SFPD, it is clear he has the San Francisco Police Department firmly focused as his target. That police department, we will attempt to show, was Ingleside Station located just off Balboa Park at San Jose Avenue.

The Zodiac Killer sent us a second set of crosshairs in the Little List letter, stating "PS. The Mt Diablo code concerns Radians + inches along the radians". This was the clue we needed.

In a previous article we highlighted a region of San Francisco for particular interest, using the following technique, but with improved map plotting and examining carefully the Phillips 66 map, it has become apparent the amended focus should be squarely over Ingleside Police Station. The phrase "PS. The Mt Diablo code concerns Radians + inches along the radians," clearly tells us to use radians as our degrees from the north axis and is "to be set to Mag.N."  So we are looking for whole radians, to which we then add in the magnetic north value of 17 degrees. This will give us our angle on the Phillips 66 map.

The​ bold circle above is sitting between the 180 and 270 degree axis. In fact, the center of the bold circle is positioned at 246 degrees. This can be confirmed using a compass rose. One radian is valued at 57.296 degrees, so four radians are valued at 4 X 57.296 = 229.184 degrees. Add in the magnetic north value of 17 degrees and our final total is 246.184 degrees. The Zodiac Killer was indicating four radians + magnetic north. He never incorporated this into the Button letter code and Phillips 66 map, telling us the crosshair was to be set to magnetic north, but a month later in the Little List letter, he added the magnetic north value in for us, seen by the positioning of the bold circle next to SFPD. Four radians and 17 degrees is 246 degrees. This bold circle is also positioned at exactly 246 degrees (see below). 

This compass rose and SFPD crosshair, angled at 246 degrees can now be placed over the Phillips 66 map. But first we will examine the second  crosshair placed at the foot of the Little List letter.

The Zodiac Killer placed 'Diablo', the Spanish word for devil over the 180 degree axis. This may not have any significance, but if we couple the 66 from Phillips 66, with the number 6 on the Phillips map crosshair, we get 666, the number of the beast. By using the same method we can add the number 66 to the 180 degrees and arrive at 180 + 66 = 246 degrees once more. Whether this was by design however, is open to question.

Let us now go ahead and superimpose the compass rose and SFPD crosshair over the Phillips 66 map (below). To be completely accurate, both have been tilted by three degrees to match the original Zodiac crosshair. (shown here).

246 degrees takes us, as the crow flies, 31 miles southwest, passing directly over the San Francisco Police Department (SFPD) of Ingleside. The map scale is 6.4 miles to the inch, so if we were traveling inches along the radians, it would be 4.84 inches. If we round off, the phrase "PS. The Mt Diablo code concerns Radians + inches along the radians," would become: "PS. The Mt Diablo code concerns four Radians + five inches along the radians". That is 229 degrees, but set to magnetic north, gives us the 246 degrees shown in the following diagrams. 

In a recent article we examined the Mount Diablo code in conjunction with the Phillips 66 road map and suggested a possibility that the Zodiac 32 Symbol cipher may have revealed San Francisco International Airport, situated at 4 radians or 229 degrees from Mount Diablo. However,  coupled with the Magnetic North value of 17 degrees at the time of mailing, was to give us a final value of 246 degrees, exactly corresponding with the bold circle the Zodiac Killer provided within his crosshairs on the 'Little List' letter mailed on July 26th 1970.  View initial article (Part One). View Part Two.
This final part of the trilogy will attempt to cement the motivation behind the Zodiac Killer's crosshairs, which he gave us on the Phillips 66 road map (as part of the Button Letter) mailed on June 26th 1970 and the 'Little List' letter one month later on July 26th 1970. In the following diagram we have incorporated the three crosshairs together to better explain the findings. This idea has been covered before, but finalizes the three part story under one banner in a little more detail.

The Zodiac Killer stated on the Button letter "The Map coupled with this code will tell you where the bomb is set". In other words, the two are to be used in conjunction with each other. This is what we did in the earlier articles, taking the code of San Francisco International Airport at 229 degrees and coupling it with the map, set at a Magnetic North value of 17 degrees, to arrive at the final value of 246 degrees.
However, this would not have been possible using the Button letter and Phillips 66 road map alone. The Zodiac Killer realizing this, gave us the two additional crosshairs on the Little List Letter, with a couple more hints. Firstly, the bold circle and secondly the phrase "PS The Mt Diablo code concerns Radians + inches along the radians". The Zodiac Killer placed this phrase over the crosshairs itself, when he could have easily accommodated both elements separately - unless of course he had an ulterior motive.

The phrase "PS The Mt Diablo code concerns Radians + inches along the radians" runs over the south axis; or to be precise, over the 180 degree axis or number 6 on the Zodiac dial. The only word bisected by this south axis is​ Diablo. 
Let us expand upon the "Map coupled with this code will tell you where the bomb is set" to better explain things, using this phrase "The Phillips 66 Map coupled with this code will tell you where the bomb is set". In the first instance, the code of San Francisco International Airport or 229 degrees was coupled with the map set to Magnetic North of 17 degrees, to equal 246 degrees. The 'Mount Diablo code' was written on the 180 degree axis, so we will couple this 180 degrees with the map (or more specifically the Phillips 66 map), to give us 180 + 66 = 246 degrees, the exact position of the bold circle he provided us in the 'Little List' letter and exactly the same as 4 radians and 17 degrees. Then we shall take the number 6 he provided on the 180 degree axis and once again couple this with the Phillips 66 map to give us 666, the mark of the Devil or Diablo.

The conventional view is that the Mount Diablo peak derives its name from the 1805 escape of several Chupcan Native Americans from the Spanish in a nearby willow thicket. The natives seemed to disappear, and the Spanish soldiers thus gave the area the name "Monte del Diablo", meaning "thicket of the devil." Diablo was placed over the 180 degree mark and the number 6 axis, and on both occasions coupled with the 66 from the Phillips 66 road map, it gave us something significant. But whether or not this was his true intention is still unclear and may never be resolved. 

Footnote: What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his 'Little List' crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.​

In a recent article we examined the Mount Diablo code in conjunction with the Phillips 66 road map and suggested the possibility that the Zodiac 32 Symbol cipher may have revealed San Francisco International Airport, situated at 4 radians or 229 degrees from Mount Diablo. However, coupled with the Magnetic North value of 17 degrees at the time of mailing, it was to give us a final value of 246 degrees, exactly corresponding with the bold circle the Zodiac Killer subsequently provided within his crosshairs on the 'Little List' letter mailed on July 26th 1970. Here we will take this one step further and see where the adjustment of the Magnetic North value of 17 degrees takes us from the airport location and see if the pinpointed location makes any sense in respect to all we think we know about the Zodiac Killer. View initial article (Part One).  

It is difficult to be exact using the Zodiac diagrams, but the angle of 246 degrees passes over the Bayview-Hunters Point region of San Francisco, situated only 5.5 miles from the Mason and Geary intersection, where it is believed Paul Stine picked up the Zodiac Killer on October 11th 1969.
Passing through the Bayview area is 3rd Street, close to Highway 101, and two possible routes Paul Stine may have traveled on his return back from San Francisco International Airport after dropping off his final paying fare, before returning back to the San Francisco theater district. The Bayview-Hunters Point region has a colorful history and has courted much controversy and conflict down the years. 
​
After a San Francisco ordinance in 1868 banned the slaughter and processing of animals within the city proper, a group of butchers established a "butchers reservation" on 81-acre of tidal marshland in the Bayview district. Within ten years, 18 slaughterhouses were located in the area along with their associated production facilities for tanning, fertilizer, wool and tallow. The "reservation" (then bounded by present-day Ingalls Street, Third Street, from Islais Creek to Bayshore) and the surrounding houses and businesses became known as Butchertown. The butcher industry declined following the 1906 San Francisco earthquake until 1971 when the final slaughterhouse closed.
Taken from Wikipedia.
​
If we insert a Zodiac timeline to this, the final slaughterhouse closed in 1971, which is the year the Zodiac mailed us his second to last confirmed correspondence on March 13th 1971 to the Los Angeles Times, before he disappeared for close to three years, the irony of which cannot be ignored. Also from our experience, we have the suggestion that the Zodiac Killer may have served in the military, or had naval connections, a common theme in Zodiac circles. The Zodiac timeline is not a certain one, predominantly because of earlier murders that may or may not be attributed to him, such as the Riverside murder of Cheri Jo Bates on October 30th 1966, nevertheless, this is where we shall start.  

Is there anything that ties Riverside, Vallejo, Benicia and the Bayview-Hunters Point in San Francisco? We shall explore some options. The Long Beach Naval Shipyard, which closed in 1997, was located at Terminal Island between the city of Long Beach and the San Pedro district of Los Angeles and was situated approximately 23 miles south of the Los Angeles International Airport. It was a 1 hr 20 minutes drive west of Riverside. The Mare Island Naval Shipyard is located in Vallejo, the hot zone highlighted by geographic profiling pioneer, Kim Rossmo, who zoomed in on a possible home location of the Zodiac Killer. And finally, the Hunters-Point Naval Shipyard, San Francisco, located on 638 acres in the southeast corner of the city. 

​At the start of World War II the Navy recognized the need for greatly increased naval shipbuilding and repair facilities in the San Francisco Bay Area, and in 1940 acquired the property from the private owners, naming it Hunters Point Naval Shipyard. The property became one of the major shipyards of the west coast. It was later renamed Treasure Island Naval Station Hunters Point Annex. During the 1940's, many workers moved into the area to work at this shipyard and other wartime related industries.
The key fissile components of the first atomic bomb were loaded onto the USS Indianapolis in July 1945 at Hunters Point for transfer to Tinian. After World War II and until 1969, the Hunters Point shipyard was the site of the Naval Radiological Defense Laboratory, the US military's largest facility for applied nuclear research. The yard was used after the war to decontaminate ships from Operation Crossroads. Because of all the testing, there is widespread radiological contamination of the site. After the war, with an influx of blue collar industry, the area remained a naval base and commercial shipyard. The Navy operated the yard until 1974, when it leased most of it to a commercial ship repair company. Extract from Wikipedia. The Navy ceased operations in 1974, the year the Zodiac mailed his final confirmed letter, the Exorcist Letter on January 29th 1974. In fact, three further potential Zodiac letters were mailed that year, before the Zodiac Killer finally disappeared for good.

The Zodiac letters definitely switched emphasis after the Paul Stine murder on October 11th 1969, from the November 9th Bus Bomb letter through to the 'Little List' letter on July 26th 1970, making references to the murder of two San Francisco police officers, Brian McDonnell on February 16th 1970 and Sgt Richard Radetich on June 19th 1970. Bombing was definitely on the agenda, although it was believed he never followed up in any of his proposed threats. 

The question remains, was irony his intention, if he had indeed selected Hunters Point as a location, somewhere he may have been familiar with or even worked. Even the surrounding areas were once known as 'Butchertown'. It should be noted that a bombing did occur in the January of 1970 at Hunters Point Police Station, highlighted in this KPIX eyewitness report - and although with near certainty it was not the Zodiac Killer, it may have been something he was aware of, had he worked in this region of San Francisco.

Did the Zodiac Killer live and work in San Francisco during the majority of his crimes, placing distance between himself and the first three attacks, before coming home to roost, or did he live across the bay in the Vallejo/Benicia areas and only used San Francisco as a mailing point on his route to work?

The 246 degrees subtended from the center point of Mount Diablo runs directly across the Hunters-Point Naval Shipyard in the Bayview District, and was consolidated by the accuracy of the 'Little List' letter crosshairs. The Mare Island Naval Shipyard has always courted some attention in Zodiac circles, on account of the proposed naval connection to our killer. Did the Zodiac Killer work at both facilities, or even the third at Riverside. Was irony at work here, or is the Hunters-Point connection just simply wide of the mark once more. 

SEE PART THREE -  http://www.zodiacciphers.com/zodiac-news/sfi-airport-hunters-point-part-three

The Zodiac Killer after killing four people in Benicia, Vallejo and Napa, suddenly switched the emphasis to the heart of San Francisco, mailing a letter to the San Francisco Chronicle on October 13th 1969, promising to target a school bus and "pick of the kiddies as they come bouncing out". In the following months came multiple references to bombs, notably in his 'My Name is' letter, detailing a bus bomb diagram and suggesting he was not responsible for wiping out "that blue meannie with a bomb". He was describing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, two months earlier, when a bomb packed with fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood. The Zodiac Killer then mailed the Dragon card on April 28th 1970 stating "I hope you enjoy yourselves when I have my blast" and then the Button Letter on June 26th 1970, cementing his connection to San Francisco by part referencing the murder of a policeman in a parked car, thought to be Officer Richard Radetich outside 643 Waller Street. In this correspondence he attached a Phillips 66 road map of San Francisco and Vicinity, stating "the map coupled with this code will tell you where the bomb is set". Then on July 26th 1970 the 'Little List' letter was mailed, including two crosshairs, one with a prominent black circle including the acronym SFPD = 0 and the second referring us back to the Button letter, stating "The Mt Diablo code concerns radians + inches along the radians". The emphasis appeared squarely over the region of San Francisco, so was the bomb the Zodiac Killer promised us, to be found somewhere in this region.

What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his 'Little List' crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.

The Zodiac Killer referred to radians (an angle of measurement), of which one radian is valued at 57.296 degrees. If we look at the prominent black circle he gave us on the 'Little List' letter (shown on the right), its center falls over the 246 degree mark on a compass rose. 246 degrees is 4 radians + 17 degrees. When the Phillips 66 road map was mailed on June 26th 1970, Magnetic North was approximately 17 degrees. 

4 radians = 4 X 57.296 = 229.184 + 17 degrees = 246 degrees.
So, apparently the Zodiac Killer had some concept of radians and the value of Magnetic North, unless we are assuming he was just lucky in his placement of the bold circle on the diagram. His further reference to SFPD (San Francisco Police Department) next to this circle, suggests this is where we should be centering our focus, bearing in mind his disdain for law enforcement.
 
The Zodiac Killer wrote "The Mt Diablo code concerns radians + inches along the radians", so let us start with complete radians. We know from above calculations that the value of 4 radians (229 degrees) is significant, so we shall place a compass rose over Mount Diablo and see where this takes us, in respect of San Francisco. 

It can be seen that 229 degrees falls on the south edge of San Francisco International Airport by Old Bayshore Highway. 
Was the Zodiac Killer intending to ratchet up the fear by exploding bombs (or the threat of bombs) in the vicinity of the airport? This seems highly unlikely, so we shall take a further look at the Button letter mailed on June 26th 1970, where the Zodiac Killer stated "The Map coupled with this code will tell you where the bomb is set. You have until next Fall to dig it up" and enter something alongside the code.

San Francisco International Airport is comprised of exactly 32 letters and fits squarely alongside the 32 symbol Button letter code. However, the 246 degree mark falls further around the circumference of the compass rose. The 4 radians took us to San Francisco International Airport, but coupled with the map "to be set to Mag.N" gives us the final value of 246 degrees. The San Francisco International Airport may have been the clue but not the final destination, which should lie in the Hunters Point region or beyond.  

SEE PART TWO - http://www.zodiacciphers.com/zodiac-news/sfi-airport-part-two-hunters-point

The Button letter was mailed on June 26th 1970 containing a footnote that stated "The map coupled with this code will tell you where the bomb is set. You have until next fall to dig it up". No bomb or any other relevant location was subsequently discovered. The Zodiac Killer's November 8th 1969 340 cipher remained "crackproof", the April 20th 1970 '13 Symbol' cipher was simply too short for any meaningful decryption, and by late July of 1970, this new '32 symbol' code and 'Phillips 66 Road Map' mailed on June 26th 1970 failed to provide little relief for an audience on the wane.