SANTA BARBARA, Calif. — In the months leading up to Friday night’s rampage which left six victims and the killer dead, there were warning signs that Elliot Rodger, a lonely and sexually frustrated college student, harbored violent tendencies.

When some young women neglected to smile at him at a bus stop one day, Rodger wrote, he splashed them with his Starbucks latte. When he saw a cluster of undergraduates frolicking happily in a park another day, Rodger grew so jealous and angry that he loaded a Super Soaker water gun with orange juice and sprayed them.

Rodger, who police say fatally shot himself after his killing spree Friday, had received treatment for years from psychologists and counselors. Last month, the 22-year-old wrote, his mother was so concerned about his well-being after seeing some of his videos on YouTube that she contacted mental health officials, who dispatched sheriff’s deputies to check on him at his apartment in Isla Vista, an enclave near the University of California at Santa Barbara.

Had the officers sensed something awry during their April 30 visit, they might have searched Rodger’s home. They would have found his three semiautomatic handguns, dozens of rounds of ammunition and a draft of his 137-page memoir-manifesto. They would have read about his plot for a “Day of Retribution” – when, as Rodger wrote, he planned to “kill everyone in Isla Vista, to utterly destroy that wretched town.”

But the deputies did not look. They concluded that Rodger seemed “quiet and timid … polite and courteous,” Santa Barbara County Sheriff Bill Brown said Sunday on CBS’s “Face the Nation.”

So they left and never returned.

“He was able to make a very convincing story that there was no problem, that he wasn’t going to hurt himself or anyone else, and he just didn’t meet the criteria for any further intervention at that point,” Brown said. “Obviously, we certainly wish that we could turn the clock back and change some things, but at the time the deputies interacted with him, he was able to convince them that he was OK.”

Simon Astaire, a friend speaking on behalf of the Rodger family, told the Los Angeles Times that minutes before the shooting Friday, Rodger emailed his manifesto to his mother and his therapist. His parents frantically raced to Isla Vista, but by the time they arrived Rodger had already killed six people and taken his own life.

Astaire told the newspaper that the family did not know Elliot had an affinity for guns, and that he was “fundamentally withdrawn,” in contrast with the confidence he displayed in his YouTube videos.

On Saturday, authorities identified three of the victims: Katherine Breann Cooper, 22, of Chino Hills, Calif.; Veronika Elizabeth Weiss, 19, of Westlake Village, Calif.; and Christopher Ross Michaels-Martinez, 20, of Los Osos, Calif.

On Sunday night, authorities identified the three remaining victims killed: Cheng Yuan Hong, 20, and George Chen, 19, both of San Jose; and Weihan Wang, 20, of Fremont, Calif. They were UCSB students who were found dead with multiple stab wounds in Rodger’s apartment. Hong and Chen are listed as tenants along with Rodger on the lease. Authorities have not determined whether Wang was another roommate or was visiting the home.

IMPORTANT CLUES MISSED

Rodger’s melee was many months in the making, and his mental state worsened throughout his adolescence, according to his writings.

But signs of his troubles, which grew increasingly frequent in recent months, failed to trigger decisive action from his mental health providers, his roommates, his longtime friends or sheriff’s deputies, who had three separate encounters with him over the past 10 months.

On UCSB’s campus, some students blamed the senseless slaughter on a systemic breakdown.

“This was premeditated,” David Ash, a 19-year-old freshman, said after Saturday night’s candlelight vigil. “He had been seeing psychologists. It definitely should’ve been prevented. But you can’t be angry. We’re just sad and mournful.”

Criminal forensic experts and mental-health professionals said authorities missed important clues. Philip Schaenman, who studies mass murders and runs a public safety research firm, said authorities should have noticed the “acceleration of red flags.”

“They get rejected by girls, they visit psychologists and social workers, their roommates say they act weirdly – taken individually, these things don’t matter much,” Schaenman said. “It’s the acceleration that’s being missed.”

Experts drew comparisons between Rodger and other mass killers, including Adam Lanza, who in 2012 fatally shot 20 small children in Newtown, Conn., and Seung Hui Cho, who in 2007 killed 32 people at Virginia Tech University. Like Rodger, Lanza and Cho killed themselves.

“We need to look at identifying people early for these disorders, rather than just identifying violence,” said Jeffrey Lieberman, chairman of psychiatry at the Columbia University College of Physicians and Surgeons. “This can be a condition that hides in plain sight.”

But James Alan Fox, a noted criminologist at Northeastern University, said: “There is no way that we can identify would-be mass murderers in advance.”

“People call them ‘red flags,’ but they’re yellow flags,” he said. “They only turn red after the blood is spilled.”

‘MY TWISTED WORLD’

In his manifesto – titled “My Twisted World” – Rodger described in graphic detail his plan to seek vengeance for his perceived societal slights. He said he wanted to target “good looking people” because he believed they were fulfilled sexually while he was not.

Rodger tells the story of his life: born in London to a British aristocrat-turned-Hollywood-director and his wife; relocated to the Los Angeles area as a young boy; lived a fulfilling childhood but was distraught by his parents’ divorce; felt ostracized as puberty hit and he struggled to woo girls; moved to Isla Vista and enrolled at Santa Barbara City College in search of a fresh start.

Last July, Rodger went to a house party in Isla Vista in what he wrote was a last-ditch effort to “give women and humanity one more chance to accept me and give me a chance to have a pleasurable youth.” If he returned home that night “a lonely virgin,” he wrote, he would plan his “Day of Retribution.”

At the party, as he stood outside with other undergraduates, he wrote, a “dark, hate-fueled rage overcame my entire being, and I tried to push as many of them as I could from the 10-foot ledge. My main target was the girls. I wanted to punish them for talking to the obnoxious boys instead of me.”

Other party guests kicked and punched Rodger, and he ended up in the hospital, where on July 21, 2013, he had his first encounter with sheriff’s deputies. Rodger wrote in his manifesto that he lied to the police, alleging that other men pushed him off the ledge. Without any evidence, the case was dismissed.

Rodger crossed paths with the sheriff’s office again Jan. 15, when he accused his roommate of stealing three candles, valued at $22. Rodger tried to make a citizen’s arrest.

By April 30, when sheriff’s deputies met with Rodger for a third time, his plan for his “ultimate showdown in the streets of Isla Vista” was well underway.

Astaire told CNN that Rodger’s parents now believe the sheriff’s deputies’ visit to their son’s apartment in April was a “missed opportunity.”