Elliot Rodger, the son of a Hollywood director, stabbed three people to death in his apartment before gunning down three more people on Friday night in the town of Isla Vista, near the campus of the University of California at Santa Barbara.
Rodger, the son of Hunger Games assistant director Peter Rodger, stalked the streets of Isla Vista in his car and on foot, firing on bystanders in a killing spree that ended when he killed himself after a shoot-out with sheriff's deputies.
Authorities found three legally purchased semi-automatic guns and more than 400 rounds of unspent ammunition in his car.
In a video posted on YouTube a young man, believed by police to be Rodger, bitterly complained of loneliness and rejection by women and outlined his plan to kill those he believed had spurned him.
"It's obviously the work of a madman," Sheriff Bill Brown told a news conference, adding that Rodger had been seen by a variety of health-care professionals and that it was "very, very apparent he was severely mentally disturbed".
Witnesses reported seeing someone in a black BMW driving through the streets and shooting at people.
At least 13 people were wounded, eight of whom were shot. The Santa Barbara Cottage Hospital said on Saturday night that six victims were still being treated in its trauma unit.
Brown said his department had been in contact with Rodger three times prior to the killings, including once after a family member asked them to check on his welfare last month.
Deputies who interviewed Rodger had found him to be polite and courteous and no further action was taken, Brown said.
"He expressed to deputies he was having difficulties with his social life and [told the deputies he] would probably not be returning to school within the next year," Brown said.