Mark Orrin Barton was born on April 2, 1955, in Stockbridge, Georgia. He grew up in a family connected to the Air Force, which meant he moved around a lot during his childhood. Barton was raised mainly in South Carolina. He went on to attend Clemson University and later the University of South Carolina.

In Atlanta, he married a woman named Debra Spivey. Together, they had two children, a son named Matthew and a daughter named Mychelle. Barton's work life took him and his family to Alabama, where his job required them to relocate. While in Alabama, Barton became increasingly paranoid and began to distrust his wife. As his work performance declined, he ultimately lost his job.

Following the loss of his job, Barton found himself in trouble with the law. He was caught sabotaging data at his former workplace and served a short jail term for this act of retaliation. Afterward, he moved back to Georgia, where he found new employment. During this time, he also began an affair with one of his wife's acquaintances.

In 1993, tragedy struck Barton’s family when his first wife, Debra Spivey, and her mother were killed. Barton became the prime suspect, but he was never charged with the crime due to a lack of evidence. He consistently denied any involvement in their deaths, a claim that authorities doubted.

Following these events, Barton received a significant insurance settlement from Debra's death. He used this money to fund a day trading career, focusing on high-risk Internet-related stocks. In 1995, he married his former mistress, Leigh Ann Vandiver. However, despite the new marriage, his mental health declined. He suffered from severe depression and paranoid delusions.

In the months leading up to significant events in his life, Barton lost a substantial amount of money in his day trading activities. His account was canceled by his trading firm after he lost $105,000.

On July 27, 1999, Mark Orrin Barton attacked his second wife, Leigh Ann Vandiver, in their home in Stockbridge, Georgia. He bludgeoned her to death while she was asleep. The following night, he killed his two children from his first marriage, Matthew and Mychelle. He covered their bodies with blankets and left notes expressing his feelings about their deaths.

Two days later, on July 29, Barton went to the Momentum Securities office in Atlanta, where he had previously worked. After a short conversation with coworkers, he suddenly pulled out two guns and began shooting. He killed four people and wounded several others. He then moved to the All-Tech Investment Group building nearby and shot five more individuals before fleeing the scene.

After the shootings, police searched Barton's home and discovered the bodies of his wife and children. They found the notes he had left behind. An extensive manhunt was launched to find him. Later that day, Barton attempted to take a young girl hostage in Kennesaw but she managed to escape and alert the authorities.

Police spotted Barton in his minivan and a chase followed. It ended at a gas station in Acworth, where Barton shot and killed himself as officers were closing in on him. In total, thirteen people lost their lives due to Barton's actions, including himself.