Elliot Rodger left clues before Santa Barbara massacre. Why did no one notice?

Elliot Rodger, the shooter in the Santa Barbara massacre, left plenty of clues about where he was headed that evening before killing six people and then himself.

There was a police report from the time he was interviewed by sheriff’s deputies when his mother had reported troubling behavior. Treatment by more than one therapist. Purchase of three legally-registered semiautomatic handguns – a Glock 34 and two Sig Sauer P226s – and more than 400 rounds of ammunition. YouTube videos of himself, strangely, desperately raging against the popular, attractive young people he had come to hate, and against his own isolation and loneliness.

And finally, a 141-page manifesto promising a “Day of Retribution,” emailed to a therapist and to his parents (who had divorced when he was in the first grade) shortly before he stabbed and killed three young men in his apartment, then drove through the Isla Vista neighborhood, shooting and killing three more people and injuring 13 others shot or hit by his black BMW coupe, which had been a gift from his mother.

He had been “forced to endure an existence of loneliness, rejection and unfulfilled desires,” he said in the video, which apparently included bullying when he was younger.

"We said right from the get-go that that kid was going to lose it someday and just freak out," a high school classmate told The New York Times. "Everyone made fun of him and stuff."

That visit from sheriff’s deputies several weeks ago might have headed off violence, particularly if they had searched Rodger’s apartment and discovered his arsenal.

But there was nothing in his behavior to suggest he was violent, and the deputies "determined he did not meet the criteria for an involuntary hold," Santa Barbara County Sheriff Bill Brown told CNN Sunday.

More is likely to emerge about Rodger’s family situation.

When one therapist alerted his mother to the emailed document, Mrs. Rodger called 911, then raced toward Santa Barbara from Los Angeles with her ex-husband, filmmaker Peter Rodger. By then it was too late and the violence had begun. No one had sufficiently connected the dots.

Doris Fuller, executive director of the Virginia-based Treatment Advocacy Center, notes that California law has provisions that permit emergency psychiatric evaluations of individuals who pose a serious threat, but that was never triggered.

Rodger's family has disclosed their son was under the care of therapists.

"Once again, we are grieving over deaths and devastation caused by a young man who was sending up red flags for danger that failed to produce intervention in time to avert tragedy," Ms. Fuller said in a statement. "In this case, the red flags were so big the killer's parents had called police … and yet the system failed.”

As evidence from before and after the rampage mounts up, so does the regret.

"Obviously, looking back on this, it's a very tragic situation and we certainly wish that we could turn the clock back and maybe change some things," Sheriff Brown told CBS's "Face the Nation" Sunday. "At the time deputies interacted with him, he was able to convince them that he was OK.”

But writing in USA Today, Northeastern University criminologist James Alan Fox says “it is virtually impossible to identify would-be mass killers before they strike.”

“There are thousands, if not tens of thousands, of citizens whose lives are not unlike Rodger's and who express the same kind of frustrations about their social isolation, yet never translate their disappointment into deadly deeds,” Professor Fox writes.

Fox also warns against becoming fascinated with – if not mesmerized by – Rodger’s videos and long manifesto.

“The real downside to the media-driven dissection of Rodger's commentaries is in the message it sends to other obscure individuals who may seek the kind of attention they have been denied for so long,” he writes. “Although well-crafted and even articulate, Rodger's words are not worthy of our continued study, at least not on the public airwaves. For the sake of understanding, we may have benefitted from the documentation offered within, but now is the time to turn attention to individuals far more deserving than he.”