Mark O. Barton was a chemist from Georgia who seemed to be going in the right direction. After graduating from college, he married his longterm girlfriend, Debra, and fathered two children, Matthew and Michelle. The family made roots in Georgia before having to move to Alabama due to Mark's employment changing. This move would be the beginning of the end for the family.
Friends and family noted that Mark became anxious, paranoid, and aggressive after the big move. He accused Debra of cheating on him, a projection, and threatened to take the children away multiple times. Debra made it a point to tell her parents how she felt about Mark and that they were growing apart. Mark was fired from his job and arrested after he tried to break in to destroy files. Eventually, Debra accused Mark of cheating on her with the 20-year-old secretary at his former place of employment. The accusation was true, and they began divorce proceedings.
In 1993, Debra and her mother, Eloise Spivey, went on a long weekend camping trip for Labor Day. They chose a campsite two hours from Debra's home in Alabama. Mark was in charge of watching the children while she was away. Debra's father, Bill Spivey, didn't hear from his wife nor his daughter after he tried contacting them. He called for a welfare check, which led to the discovery of their murders. Two witnesses claimed to have seen a tall man jogging away from the camper that the duo had rented. When Bill called Mark to tell him the news, Mark seemed unamused and unemotional.
Despite Mark's bizarre composure, changing stories, and insistence of never having been to that campsite, he was never fully investigated. Mark first claimed that he was at home the entire day spending time with his children. Then, a neighbor said that she saw Mark's car leave the driveway at around 4:30 in the afternoon, and arriving back at midnight. Mark then changed his story and said that he went to a movie and a restaurant. After failing to produce receipts, he said that he was job hunting. After that, he rescinded his statements. Apparently, he left the children with his mistress, Leigh Ann Vandiver. DNA testing in 1993 was not as advanced, and even though they found DNA under Debra's fingerprints, they could not pin Mark to the murder.
Mark and Leigh Anne got married in 1995. Leigh Ann was interviewed by the investigators and complied more than Mark did. She even admitted that his behavior "bothered" her every now and then but she wasn't worried. When an investigator told her that she needed to leave if she felt unsafe and that they could help her, she quickly left and was never seen by them again. Sadly, she never took them up on their offer which sealed her fate.
By 1999, Mark had already peaked and crashed in a new career: day-trading. He recieved $600,000 in Debra's life insurance policy and decided to try and invest it in day-trading. He worked with Momentum Securities and All-Tech before being let go from both companies within one year of each other. This was officially his breaking point.
On July 29, 1999, Mark entered All-Tech's office to see his old pal Brent Doonan. Brent was happy to see his former coworker and friend. They didn't leave things on the best of terms as Brent was the one who had to tell Mark that he was being let go. Mark invited Brent into a conference room alone to show him something. When Brent entered the room, Mark shut the door and closed the blinds leading into the room.
"Today," Mark said, "is going to be visual..." Before Brent could react, Mark took out two handguns and blindly shot at Brent. After Brent went down, Mark turned his sights on the other office workers, shooting into the room randomly. Mark attempted to shoot at Nell Jones, who was sitting at her computer, but Brent came out of nowhere and tackled him. This helped multiple people flee. Police and SWAT arrived, but Mark had left. He killed five people in that office. Before that, he had gone to All-Tech and murdered 4 people, including one of his former managers.
Police ended up cornering Mark in his van but couldn't get to him before he committed suicide. The police went to the family's apartment where they found 27-year-old Leigh Ann, 11-year-old Matthew, and 8-year-old Michelle bludgeoned to death. He left notes all around the apartment claiming that Leigh Ann was the source of all of his problems and that the children needed to die so they did not have to live with the burden of what he was going to do.
All in all, he killed 14 people: Leigh Ann Vandiver Barton, 27, Matthew Barton, 1,1 Michelle Barton, 8, Russell J. Brown, 42, Dean Delawalla, 52, Joseph J. Dessert, 60, Kevin Dial, 38, Jamshid Havash, 45, Vadewattee Muralidhara, 44, Allen Charles Tenenbaum, 48, Edward Quinn, 58, Scott A. Webb, 30, Debra Barton, 36, Eloise Spivey, 59. Bill Spivey blames investigators for the senseless deaths, "twelve more people wouldn't have died at his hands" if they decided to investigate him fully. Brent Doonan survived the attack and helped write a book on the event titled Murder at the Office. He left multiple people with life-long injuries. One of his injured victims committed suicide years later, technically bringing his murder count to 15.