Classic beta-male rage
For investigators searching for his path to mass murder, he left behind a typewritten manifesto at the scene and a string of on-line postings that showed he had become increasingly interested in other high-profile shootings, angry at not having a girlfriend and bitter at a world that he believed was working against him.
Angry about not having a girlfriend, a classic case of beta-male rage (although in a three-way alpha-beta-omega classification system, it would be omega-male rage).
And there’s further confirmation that Chris Harper-Mercer had Asperger’s Syndrome (or that at least his mother thought he had that):
[Chris’ mother] apparently contributed to online forums dealing with health issues. In one exchange, a writer who appears to be Ms. Harper offered assistance to the mother of a child with Asperger’s syndrome, saying, “I’m a nurse and also have an Aspergers kid.”
The article also says he wore the same outfit every day (aspies like routine) and that he would spend hours talking about guns if someone was willing to listen (aspies will talk endlessly about their special interests).