In a written but unpublished post to his blog, the 48-year-old gunman wrote that if a particular woman he admired from afar would be his girlfriend, he would "cancel this plan or put [it] on hold, at least for a while," ABC News has learned through an analysis of his blog's hidden source code.
"At the gym I saw a woman I like. I see her at the park and ride sometimes, so she isn't a stranger. Occationaly [sic] she makes good eye contact and smiles, etc. She is maybe 40ish, and attractive to me," Sodini wrote on his blog and then hid from public view with a veil of computer code.
"I made brief conversation to her and a younger woman she was with today. To get a friend like her (and for night time action) I would cancel this plan, or put on hold, at least for a while," he wrote.
The identity of the woman -- and whether she was in the gym when Sodini came in shooting -- remains unknown and will perhaps stay that way forever, given that Sodini took his own life in the shooting.
It's unknown when the the blog entry -- obscured from public view with code or "commented out" -- was written. The last known published entry was on Aug. 3, in which Sodini wrote he will spend the next day "practic[ing] my routine and make sure it is well polished." Also on Aug. 3, he wrote that he "will try not to add anymore entries because this computer clicking distracts me."
It is also unknown why Sodini would have written the entry and then hidden it from public view.
So much of Sodini's personal life, his psychology and plans for the murders were laid bare in the blog, which he registered in 2000.
On Aug. 4, Sodini entered the LA Fitness club in Collier Township, Pa. and, using two 9 mm automatic pistols, fired 36 shots inside an aerobics class of about 30 women. He then used a .45-caliber revolver to take his own life. An unused .32 caliber semi-automatic pistol was later found in Sodini's pocket, police said.
"In our opinion, there was nobody in that club that could have done anything that could have prevented Sodini from committing this act," Allegheny County Police Superintendent Charles Moffatt said. "He was hell-bent. ... He just had a lot of hatred in him."
Police found two typed notes in Sodini's bag at the scene, each reflecting his extreme frustration and depression with women. He complained of "never having spent a weekend with a woman," a theme shared in the numerous chilling blog posts he wrote prior to the shooting.
The diary also indicated that Sodini hadn't had sex since 1990 and that his so-called "practice papers" -- details about the planning of the attack -- are welcome to be published afterward because "maybe all this will shed insight on why some people just cannot make things happen in their life, which can potentially benefit others."
The image that emerges from his blog is that of a loner -- a psychopath, routinely rejected by women -- who spent a year casing the gym and plotting his revenge on "the young girls here [that] look so beautiful as to not be human, very edible."
A combination of feelings of neglect, loneliness, insanity and perhaps a fear of losing his job may have all contributed to what set off Sodini, a seemingly by-the-book computer programmer with a well-paying job in Pittsburgh, experts said.
The loner, who feels he was neglected as a child and seeks attention through killing, fits the classic profile for a mass shooter, law enforcement officials said. Forensic psychologists who study killers told ABCNews.com that, judging from Sodini's writings, he was likely severely depressed and felt that the shooting was the one way he could garner people's interest in him.
"These are the rambling messages of a likely psychotic and display characteristics of a man who has been severely depressed for a long time," forensic psychologist Naftali Berrill said of Sodini's writings.