(CNN) -- George Sodini, the man who killed three women and wounded nine others before killing himself Tuesday at a Pennsylvania fitness center, showed in his writings typical characteristics of a mass murderer, experts say.
George Sodini failed at every relationship but couldn't blame himself, experts say.
"What distinguishes the mass murderer who takes his own life afterwards from the person who just commits suicide is the externalization of blame," said James Alan Fox, a Northeastern University professor of criminal justice and author of six books on mass murder.
"If you blame yourself for your problems, then maybe you direct your violence inwardly. If you blame other people for your failures, like Sodini did, you go after those people."
Sodini's blog vents his frustration and rage at the lack of relationships and sex in his life, and he blames all women for letting him down.
Although Sodini expressed intense hatred for his brother and father, "it also didn't surprise me in this case that he made some derogatory comments about his mother," said Dr. J. Reid Meloy, a forensic psychologist and clinical professor of psychiatry at the University of California, San Diego. "A lot of times, when there's this level of hatred against women, there's also a very antagonistic relationship with the mother, but it gets shifted onto other women." Watch what Sodini reveals about himself on video »
Sodini did not target specific women who had hurt him but all women, Fox said.
"He had an issue with women who were not giving him the time of day -- all these young, beautiful, attractive, healthy, fit women at the health club," Fox said. "And so he specifically chose the health club, not just some random spot, to go after the people he blamed."
Mass killers feel that they have been victimized and that their actions are justified, Fox and Meloy said.
"They've been victimized by someone at work, by someone in the family, by the world in general; they've been dealt a bad hand," Fox said. "And ... they feel at the very end they can stand up -- with a gun -- and restore that power imbalance. They often see the gun as the great equalizer.
"This act, this final act of murder, is a way to leave this world feeling some degree of satisfaction of, in the end, being the last one to have the best and last laugh," Fox said. See a timeline of mass shootings since 2005 »
"The concept here is really, really hard for most people to grasp, and that is the sense of entitlement, that 'I have a right to murder all of these women because of my personal frustration,' " Meloy said. "It's absolutely astonishing that a person can come to that mind-set."
Neither expert treated Sodini, but both noted that Sodini's act, like most mass murders, was anything but spontaneous.
"His blog is a striking example of how mass murders are planned, relatively carefully planned, over the course of days, weeks or, in this case, months," Meloy said.
"There's this myth that mass killers just snap and go berserk and suddenly, without warning, shoot indiscriminately," Fox said. "Well, he had been thinking about this for some time. He had originally planned to commit the mass murder in January [but] 'chickened out,' as he said. But this shows a lot of methodical planning, thinking."
That hesitation, as well as his possible hesitation on the day of the killings, is unusual, Meloy said.
"Typically, as these guys are doing it, they have no ambivalence," he said. "The have made the decision to maximize casualties and to also kill themselves, as he did."
Often some humiliating event "starts the clock" and sets long-laid plans in motion, Meloy said, but he didn't see evidence of such an incident in the hours or days before Sodini's rampage.
"These guys are very narcissistically sensitive, meaning that the kind of insult or slight that you or I would just fluff off, these guys will ruminate and think about it and do that for long periods of time," Meloy said.
Sodini was not a bad-looking man; he was intelligent and had a good job, so his failure to attract women must have had something to do with his behavior, Meloy said. But Sodini couldn't see that.
"He had difficult and unhappy and unsuccessful relationships with everybody," Fox said. "What he was never able to do was to see that perhaps the problem was him. Maybe there's a reason why everybody rejects him, no one wants to be close to him. Maybe it's something about his own personality.
"But mass murderers don't look at things that way. If they saw themselves as being the culprit, perhaps they would just commit suicide. But no. Everyone else is to blame."