Mark Orrin Barton (April 2, 1955 – July 29, 1999) was a spree killer from Stockbridge, Georgia, who killed 12 people and injured 13 more on July 29, 1999. The murders occurred at Barton's home as well as at two Atlanta day trading firms that had employed him previously as a day trader, Momentum Securities and the All-Tech Investment Group. It is believed that Barton was motivated by large financial losses during the previous two months. Barton killed himself before he could be apprehended by police.