The Zodiac Killer was a serial killer who operated in Northern California in the late 1960s and early 1970s. He claimed to have killed 37 victims, though police only confirmed seven killings. He taunted police and the public by sending encrypted letters with clues to his identity but was never caught. Some key facts are that he committed crimes in the San Francisco Bay area, left DNA evidence on stamps of taunting letters, and was likely a psychopath who enjoyed attention but blended in to avoid capture.