morbidology:This Halloween card was sent to journalist Paul Avery of the San Francisco Chronicle on October 27, 1970, by the notorious Zodiac Killer. Inside, the killer scrawled eerie messages and wordplay, including “Peek-a-boo, you are doomed,” along with a strange symbol resembling his signature crosshair. It hinted at new threats and deepened the chilling cat-and-mouse game with police and media.