Mark O. Barton

An intensive manhunt ensued. Four hours after the All-Tech Investment Group shooting, Barton accosted and threatened a young girl in Kennesaw, apparently attempting to secure a hostage for his escape. The young girl escaped and called police. Responding police officers spotted Barton in his minivan and a chase ensued, culminating at a gas station in Acworth. As law enforcement attempted to apprehend him, Barton shot and killed himself. On July 29, 2009, Atlanta, GA marked the 10th anniversary of the tragedy. On July 29, 2019, Atlanta, GA marked the 20th anniversary of the tragedy.

On July 27, 1999, Barton woke up early in the morning and bludgeoned Leigh Ann to death as she slept. The next night, he also beat his children Matthew and Mychelle to death. He covered them with blankets and left notes on their bodies, reading in part:

Before the massacre, Barton was a suspect in the 1993 beating deaths of his first wife Debra Spivey and her mother Eloise Spivey in Cherokee County, Alabama; however, he was never charged for their murders and always denied having had any part in them, including in the note he left behind with the bodies of his children and his second wife. Notwithstanding his denials, authorities still consider Barton a suspect in the 1993 murders.

The family moved to Alabama as Barton's employer required him there. Barton grew paranoid and started distrusting his own wife. He lost his employment after his performance plummeted. He was also caught sabotaging data of the company that had fired him and served a short jail term for this retaliatory act. Barton found a new employer in Georgia and a mistress in one of his wife's acquaintances, Leigh Ann Vandiver, with whom he had an affair. In 1993, Spivey and her mother Eloise were killed by bludgeoning. Barton was the prime suspect in the double-murder, but was not charged due to the lack of evidence. Barton made Leigh Ann his wife in 1995. His mental health continued to deteriorate, however, and he began to suffer from both severe depression and paranoid delusions.

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 died by his own hand before he could be apprehended by police.

Barton was born on April 2, 1955, in Stockbridge, Georgia, to an Air Force family and was raised in South Carolina. Barton attended Clemson University and the University of South Carolina, where he earned a degree in chemistry despite an ongoing drug habit. Back in Atlanta, he married Debra Spivey, with whom he had two children named Matthew and Mychelle.