Authorities who visited a 22-year-old Isla Vista man three weeks before he allegedly killed six
Knowledge of the purchases might have prompted the five Santa Barbara County sheriff's deputies to search Elliot Rodger's apartment and discover guns he claimed in a video to have bought for the May 23 rampage.
But the deputies merely interviewed Rodger outside his apartment and did not take any further action, according to the Reuters news service.
"The issue of weapons did not come up," sheriff's spokeswoman Kelly Hoover told the Los Angeles Times newspaper, Reuters said.
"We had no information that he had weapons or reason to believe he had weapons," she said.
The April 30 welfare check, prompted by a call from a county mental health worker concerned about videos Rodger had posted on YouTube, was the third contact police had with Rodger in the past 12 months.
But police who met with Rodger to ask about the videos found him "timid and polite," and did not consider him a threat to others, Reuters said.
"They did not view the videos or conduct a weapons check on Rodger," a statement from the sheriff's office said.
Rodger later sent a 137-page manifesto to his parents, therapist and a few others that said he feared the police visit was about to foil his plans for the killing spree.
"I had the striking and devastating fear that someone had somehow discovered what I was planning to do, and reported me for it," Rodger said in the document.
"If that was the case, the police would have searched my room, found all of my guns and weapons, along with my writings about what I plan to do with them," he said.
The county sheriff's department maintains its officers acted professionally and within state law and department policies, Reuters said.