The Zodiac serial killer claimed to have murdered 37 people in Northern California during the Sixties and Seventies. However, only five murder victims have been officially confirmed.

Zodiac’s name derives from at least 18 taunting letters and postcards sent to the Vallejo Times-Herald, the San Francisco Chronicle and the San Francisco Examiner, as well as to police, claiming responsibility for a number of murders.

Zodiac also sent police cryptograms, four in total and three of which are still unsolved. The first, sent in 1969 to the Vallejo Times-Herald and translated days later, began: “I like killing people because it is so much fun.”

Many of the killer’s letters and postcards begin: “This is the Zodiac speaking . . .” The origin of the name Zodiac is unknown. The letters often threatened further killings unless newspaper editors printed them in full.

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In one letter Zodiac bragged to police that he had chatted with officers three minutes after killing someone, while in another he threatened to blow up a school bus full of children, although he never carried out this threat.

In a letter in April 1970 the killer wrote his name using a code of 13 symbols. However, his identity is still unknown.

Arthur Leigh Allen, a primary school teacher, was the only suspect to be formally investigated by police out of thousands whose names came up over the years. It was alleged that he was in the area on the night that Cheri Jo Bates, an unconfirmed Zodiac victim, died.

Two letters from Zodiac featured a symbol at the bottom resembling the number 32, Allen’s age at the time of several of the killings, and his door number, 32 Fresno Street.

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