The Zodiac Killer is the pseudonym of an American serial killer1 who operated in Northern California from at least the late 1960s to the early 1970s. The unidentified killer originated the name in a series of taunting letters and cards sent to the San Francisco Bay Area press. These letters included four cryptograms. The Zodiac murdered five known victims in Benicia, Vallejo, Napa County, and San Francisco, respectively, between December 1968 and October 1969. He targeted young couples, with two of the men surviving attempted murder. He also murdered a male cab driver. The Zodiac himself once claimed to have murdered 37 victims, and he has been linked to several other cold cases.