Between February 28, 1975 and May 13, 1976 at least 23 female residents of New York's Westchester County were wounded by one-inch steel darts, fired by an unknown assailant armed with an air gun. All the victims lived in ground-floor apartments, and each was wounded in the head, neck or chest by the projectiles fired through windows. No suspects was identified in the case, and police lost interest two months after the final attack when a gunman calling himself The Son of Sam brought terror to New York city. The Westchester "Dartman" remained at large.
Journalist Maury Terry, investigating alleged satanic connections in the "Sam" case, discovered that the Dartman was a symbol of death in 15th century Europe. It made a tantalizing lead, combined with reports of cult gatherings, canine sacrifices and ritual gang rapes in Westchester County, but without a suspect or a solid lead the case went cold. A similar series of woundings, blamed on an unknown blowgun sniper, were reported from Washington in the spring of 2002. That case also remains unsolved.
Source: The Encyclopedia of Unsolved Crimes