I think this article is leaning in the right direction: mental illness is the cause of mass shootings; not guns, parents, television, games.
Actually, it’s the response to mental illness. I was reading a Reddit post where someone said their OCD made them take 2 hour showers. MADE them. They had no choice. They had to do it and were powerless to stop.
So this guy’s illness made him shoot those people. He believes he is as much of a victim as them. So when he locked and loaded and drove 9 hours to that mall, he was unable to keep from doing it...in his eyes and the eyes of his enablers.