Hey, look what I have found for you, everything you ever wanted to know about the Zodiac killer, but were too lazy to find it for yourself:
http://www.zodiackiller.com/AllenFile.html
According to his brother, Ron, Allen was given a Zodiac watch as a Christmas gift from their mother in 1967. (Allen's estimation of when he received the watch was July or August 1969.) The logo for the Zodiac watch is a cross-circle symbol, the same as eventually used by the Zodiac killer.
According to police statements, within days of receiving the watch, Allen is alleged to have made these claims to his friend, Don Cheney:
(Allen used the premise of writing a novel to communicate this fantasy. Cheney estimates the conversation took place on Jan. 1, 1969.)
He would like to kill couples at random.
He would taunt the police with letters detailing his crimes.
He would sign the letters with the cross-circle symbol from his watch.
He would call himself "Zodiac."
He would wear make-up to change his appearance.
He would attach a flashlight to the barrel of his gun in order to shoot at night.
He would fool women into stopping their cars in rural areas by claiming they had problems with their tires, then loosen their lug nuts and eventually take them captive.
Don eventually took this information to the police and, in 1972,....
What do you think? Damn good circumstancial evidence....