His letters were signed off with what looked like a Z symbol, but as yet authorities were a long way from finding out, this may have been the very inception of the Zodiac, the 'calm' before the storm of Lake Herman Road and beyond.
What, if anything, lies within the Confession Letter to suggest this declaration of murder was in any way related to the other crimes that began on December 20th 1968, just over two years later.
It has been previously pointed out that the author of the 'Confession' letter used the wording "She squirmed and shook as I choaked her. And her lips twiched". This having striking similarities to the 'Little List' letter the Zodiac Killer mailed on July 26th 1970, in which he stated "Some I shall tie over ant hills and watch them scream + twich and squirm."
But more apparent is the egocentric nature displayed in the 'Confession' letter, that he maintains throughout his correspondence to the authorities, right through to the Exorcist Letter mailed on January 29th 1974, revealing character patterns of his own unique writing style. His extreme use of the word 'I' appears no less than 19 times, along with his use of 'me', 'my' or 'mine', a further 12 times in this short letter comprising of 423 words. So in total, a reference to himself appears 31 times. That is 7.33% or once every 14 words, and something we were going to get accustomed to over the following eight years.
The 'Bus Bomb' letter, 'Little List' letter and 'Melvin Belli' letter are further examples of the Zodiac Killer's compunction to constantly refer to himself as the focus of attention within his writings. In the Melvin Belli Letter this occurs 16 times, within the body of text containing 134 words, that is 11.94%. The Little List Letter contains 12 in 178 words, at 10.07% and the Bus Bomb Letter is equally high in frequency.
When the 408 Cipher was unraveled by Donald Gene and Bettye June Harden a short time after it was received, the author revealed his 'Most Dangerous Game', believed to have been inspired by a book published on January 19th 1924 by Richard Connell. The short story describes a hunter, who disillusioned with tracking down animals, turns to the more thrilling experience of hunting humans instead.
This early 'Confession' letter may have been the precursor to the 408 Cipher and the early thought processes of the man soon to become the Zodiac Killer, when he typed "I AM NOT INSANE. BUT THAT WILL NOT STOP THE GAME" and finishing off with "I AM STALKING YOUR GIRLS NOW."
In the Dripping Pen Card and 340 Cipher the Zodiac Killer appears to hand us a chronological timeline of his murders. He refers to December, July, August, September and October = 7.
If indeed it was chronological, then five murders would be accounted for, leaving two murders in August unexplained.
However, if the Bus Bomb diagram was not referring to murder zones, then that leaves us another option for the months of December, July, August, September and October, indicated on the Dripping Pen Card.
The murders of Betty Lou Jensen and David Faraday in December, Darlene Ferrin in July, Cecelia Shepard in September and the murders of Paul Stine and Cheri Jo Bates, both in October, would now leave six murders of the seven accounted for and cementing the Riverside attack as a Zodiac crime. The seventh victim would still be, as yet undetermined. The Hood and Garcia murders would still remain a possibility, since they occurred on February 21st 1970, with the Domingos and Edwards murders on June 4th 1963 falling into the 'Pre-Zodiac' timeline, but not completely ruled out on this basis.
The Zodiac Killer in the 'Los Angeles' letter on March 13th 1971 claimed "I do have to give them credit for stumbling across my riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there."
This may or may not be the case, but the murder of Cheri Jo Bates on October 30th 1966 is one crime, that in many respects has the hallmark of the Zodiac Killer stamped all over it.