Sodini was a 48-year-old systems analyst at the law firm of K&L Gates and a resident of Scott Township. He had written about contemplating carrying out a shooting, which he referred to as the "exit plan", while also revealing that he "chickened out" of carrying out such a shooting earlier in the year. His website states that he was "never married" and concludes "Death Lives!" Sodini states, "Probably 99% of the people who know me well don't even think I was this crazy." Sodini is reported to have left a note inside the gym bag stating his hatred for women. Nearly a week after the murders, it was revealed that Sodini had brought an inert grenade on a Port Authority bus on July 28, 2009. After a passenger sitting next to him notified police, he was questioned about the incident but no charges were filed.
On a website registered in his name, Sodini chronicled over a nine-month period his rejections by women and his severe sexual frustration. "Who knows why? I am not ugly or too weird. No sex since July 1990 either (I was 29)", he writes. "Last time I slept all night with a girlfriend it was 1982. Girls and women don't even give me a second look ANYWHERE". About his problems with women, he wrote: "Women just don't like me. There are 30 million desirable women in the US (my estimate) and I cannot find one". In 2008, Sodini posted online videos, in which he discusses his emotions, along with a tour of his home, the latter which was a homework assignment from "a self-help seminar [he] had attended on how to date women".
The shooting occurred at a women's aerobics class at the LA Fitness center at approximately 8:15 p.m. The shooter entered the class, placed a duffel bag on the ground, turned off the lights, took out two handguns and began firing, police said. According to police, the gunman fired 52 shots with two Glock 9×19mm semiautomatic pistols before committing suicide by shooting himself in the head with a .45-caliber revolver. A .32-caliber semiautomatic pistol found in his pocket was not used.
Three women and the gunman died, and about nine other people were injured. The Allegheny County Medical Examiner's office identified the three women who died as Heidi Overmier, 46, of Collier Township; Elizabeth Gannon, 49, of Green Tree, Pennsylvania; and Jody Billingsley, 38, of Mt. Lebanon, Pennsylvania.