Zodiac Killer is the nickname given to an unidentified serial killer who operated in northern California in the late 1960s and early 1970s. The Zodiac murdered victims in Benicia, Vallejo, Lake Berryessa, and San Francisco between December 1968 and October 1969. Four men and three women between the ages of 16 and 29 were targeted. The killer originated the name "Zodiac" in an August 7, 1969 letter to the local Bay Area press, which was just one in a series of taunting letters. These letters included four cryptograms (or ciphers). Of the four cryptograms sent, only one has been definitively solved.