I agree with the general point that a vast infrastructure of mental health resources that are affordable, available, and unstigmatized would surely succeed in preventing many of these rampages.
Here, though, it looks like there was some intervention, that he was in treatment with multiple therapists, and that his own parents had reported his alarming youtube videos to the police.
Rodger was getting mental help. His parents reportedly saw his dozens of YouTube videos — of him wandering alone or sitting in his car complaining about the world’s unfairness, his loneliness and a desire for vengeance — and were concerned enough to report them to police, their lawyer tells ABC News. He was being was being treated by multiple therapists, according to the lawyer, and had been diagnosed as “a high-functioning patient with Asperger syndrome.”
Here's the transcript of the last video:
"On the day of retribution, I am going to enter the hottest sorority house at UCSB and I will slaughter every single spoiled, stuck-up, blond slut I see inside there. All those girls I've desired so much. They have all rejected me and looked down on me as an inferior man if I ever made a sexual advance toward them, while they throw themselves at these obnoxious brutes.
"I take great pleasure in slaughtering all of you., You will finally see that I am, in truth, the superior one, the true alpha male. [laughs] Yes, after I have annihilated every single girl in the sorority house, I'll take to the streets of Isla Vista and slay every single person I see there. All those popular kids who live such lives of hedonistic pleasure while I've had to rot in loneliness all these years. They all look down upon me every time I tried to join them, they've all treated me like a mouse.