The gunman, identified by police as 48-year-old George Sodini, wrote often in his diary of his perception that women disliked him and how he was lonely, reports CBS station KDKA.
In a May 18, 2009, entry Sodini says, "Women just don't like me. There are 30 million desirable women in the U.S. and I cannot find one. KDKA reports.
Sodini sprayed bullets into a fitness class filled with women, killing three and then himself Tuesday night. He kept a Web page in which he talks of an earlier plan for violence at the gym in which he said he "chickened out."
The full online diary is here.
At a press conference this afternoon, police announced that the gunman had no relationship to any of the victims. He had four guns with him, but used only three.
In an entry dated January 6, 2009, the author, a 48-year-old white male, writes, "I can do this ... God have mercy ... I wish life could be better ... I wish I had answers ... Bye."
Two hours after that entry, he wrote: "I chickened out ... I brought the loaded guns, everything."
Then, this past Sunday, Aug. 2, the man wrote: "Tomorrow is the big day ... Last time I tried this, I chickened out. Let's see how this new approach works out."
Allusions to a shooting begin as far back as November of last year: "Why do this to young girls?" he asks.
Richard Walker, who was playing basketball near the exercise room when shots rang out, said he carried one victim who was shot in the leg outside to paramedics.
"She just said, 'He's gonna kill me,'" Walker told CBS' "The Early Show". "It was horrible."
Neighbors described Sodini as anti-social, and the Web page in his name showcased a resume setting forth his credentials as an unhappy loner. It listed his date of death - Aug. 4, 2009 - and his status of "Never married." The page ended with the words "Death Lives!"
On Tuesday night, the gunman walked into the fitness center, entered a "Latin impact" dance aerobics class and placed a duffel bag on the ground. After pausing a few moments, he took at least two guns out of the bag and started shooting.
Three women were killed and nine people were injured. Police say he may have fired as many as 52 shots before turning the gun on himself and committing suicide.
"He walked right into the room where the shootings occurred as if he knew exactly where he was going," Allegheny County police Superintendent Charles Moffatt said. "I think he went in with the idea of doing what he did."
Authorities on Wednesday identified the gunman as Sodini, of nearby Scott Township. The three women who died were Heidi Overmier, 46, of Carnegie; Elizabeth Gannon, 49, of Pittsburgh; and Jody Billingsley, 38, of Mount Lebanon.
The 4,610-word Web page, on a domain registered in Sodini's name, appeared to be a nine-month chronology of his plans to commit the shooting, his decision to delay it and the process that led to the eventual carnage at the health club Tuesday. Authorities did not immediately confirm that the site belonged to Sodini, but the elaborate nature of the comments suggested authenticity.
"The biggest problem of all is not having relationships or friends, but not being able to achieve and acquire what I desire in those or many other areas," said an entry dated Sunday. "Everthing stays the same regardless of the effert I put in. If I had control over my life then I would be happier. But for about the past 30 years, I have not."
The Web site's author wrote of planning the attack since at least November, and had tried to do it when the same Tuesday-night dance aerobics class he targeted met on Jan. 6.
"It is 8:45PM: I chickened out!" he wrote. "I brought the loaded guns, everything. Hell!"
A neighbor of Sodini's, Connie Fontanesi, said she was interviewed by county detectives Tuesday evening.
"He was so anti-social we really didn't learn anything personal about him," she said.
Picking up on Sodini's alleged frustrations with women, a diary entry on May 26, 2009, reads: "I was invited to a picnic, and I went. An older woman there, out of the blue, asked if I liked high school. Then, quickly asked if I was picked on very much. Interesting why she would ask that. But, thanks, I already know what the problem is, but a solution eludes me," KDKA reports.
The violence rocked the suburban Pittsburgh town of about 5,300 residents some eight miles southwest of downtown.
Joann Gazzam, a member of the weekly dance aerobics class, saw the gunman walk to the back of the room near some weights, set down a bag and fumble with it for a few minutes before coming up with what appeared to be two guns and opening fire, according to her sister, Debi Wozniak, of suburban Dormont.
Gazzam told Wozniak that the instructor was among those who appeared to have been shot.
"She told me, 'Debi, I seen everything. Oh, my God, I seen everything. I seen him pull out the guns,"' said Wozniak, who usually attends the class every Tuesday from 8 p.m. to 9 p.m. but was running late and didn't make it. Police say the shooting happened about 8:15 p.m.
The clean-shaven gunman walked in the room wearing workout gear, turned off the lights and, at first nobody knew what was happening, said Stacey Falk, 26, of Bridgeville, who was in the class.
"All of us girls were just ducking behind each other and it was just, you know, I was behind a girl, one of the girls in front to get hit, and when he was in the opposite corner shooting, I booked it," she told WPXI-TV.
The gunman went into the health club planning to shoot several people - firing "multiple" weapons "indiscriminately" - and didn't say anything before unleashing a burst of bullets, Moffatt said. Moffatt said police recovered at least two guns from the scene and a note from the shooter's duffel bag, but he would not say who wrote it.
"I don't think anyone could have stopped him," Moffatt said.
Five of the wounded victims arrived in critical condition at UPMC Mercy Hospital, but three of them were upgraded to serious condition by early Wednesday. Two women remained in fair condition at another Pittsburgh hospital. One victim was treated and released for a shoulder wound and a woman with a bullet wound to the knee remained in stable condition Wednesday.
Loretta Moss, 44, of McDonald, said she was exercising on a treadmill when she heard a popping noise.
"I didn't pay any attention, and the next minute, people were screaming," said Moss, who had come to the gym Tuesday night for the first time in a couple of weeks. She said she then heard more pops.
"There was like a whole spray of them. I'd say about 15 altogether, and then people started screaming and yelling and started running out the building," she said.
"We laid down, and then after the last set of ... gunshots, we got up, and someone said, 'run."'