The parents of British-born Elliot Rodger desperately searched for him as he carried out a deadly gun and knife rampage in Santa Barbara, California, after they received his chilling manifesto, according to a family friend.
Rodger, 22, emailed a 140-page document to several people, including his parents and therapist, just before the shootings began in the town of Isla Vista on Friday night, family friend Simon Astaire told CNN.
Rodger is believed to have shot himself in his car after killing six people with a gun and knife and fighting two gun battles with police.
The manifesto details his rejection by women and his fury at men who find it easy to attract the opposite sex. It also chronicles his distress about his height, appearance and his parents' divorce.
Rodger's mother, Lichin, saw the email at 9.17pm local time and immediately went to her son's YouTube page, where she saw a video entitled "Retribution," that he posted on the day of the killings, Mr Astaire told CNN.
In the video, Rodger spoke of his plan to "slaughter" women at a sorority house at the University of California at Santa Barbara.
Mr Astaire told the news network Rodger's mother called his father Peter, a Hollywood film-maker, before calling 911 and the parents set off for Santa Barbara from Los Angeles.
On the way to the seaside town they heard there was a shooting and later that night, they found out their son was behind the violence, the family friend said.
Santa Barbara Sheriff Bill Brown said the student stabbed three men to death in his apartment before killing three more people in a shooting spree, leaving 13 injured.
It ended when Rodger slammed into a parked vehicle and apparently shot himself in the head, police said.
Among the dead were two women, aged 19 and 22, who were gunned down outside a university sorority house and a male student who was shot in a delicatessen.
Police described the spree as "premeditated mass murder".
The shootings began at 9.30pm local time on Friday, just minutes after Rodger's mother read the manifesto.
Rodger, who had Asperger's syndrome, opened fire at random as he drove around the beach community near the University of California campus.
Mr Brown said it was a "chaotic, rapidly unfolding and convoluted incident" across 10 separate locations.
Rodger was found with three 9mm semi-automatic guns in his car and more than 400 rounds of unused ammunition, and Mr Brown said he had "no doubt there would have been further loss of life" if police had not intervened.
Around 3,000 students gathered for a vigil to remember the dead on the University of California's Santa Barbara campus.
Many of them held candles during the emotional event.
The Rodger family's lawyer, Alan Shifman, revealed that they called police several weeks ago after being alarmed that the future killer had uploaded several YouTube videos "regarding suicide and the killing of people".
Police interviewed him at his home but found him to be a "perfectly polite, kind and wonderful human", Mr Shifman said.
Rodger had posted videos and written blogs saying he would carry out the killings because he was a virgin and had never kissed a girl.
The "Retribution" YouTube video shows Rodger sat in his car, looking directly at the camera and declaring "the day of retribution" was coming. He describes plans to shoot women and promises retribution for his "loneliness and frustration" at never having had a girlfriend.
The student went on: "For the last eight years of my life, ever since I hit puberty, I've been forced to endure an existence of loneliness, rejection and unfulfilled desires all because girls have never been attracted to me."
Rodger said: "All you popular kids, you've never accepted me and now you'll pay for it."
He went on: "I'll take great pleasure in slaughtering all of you. You will finally see that I am, in truth, the superior one, the true alpha male."
On his blog, Rodger wrote that he was born in the UK and moved to the United States when he was five.
In a post dated April 16, he wrote: "Being lonely in a beautiful place like Santa Barbara is truly a horrible experience.
"As I've said many times, a beautiful environment can be the darkest hell if you have to experience it all alone, especially while having to watch other men walking around with their girlfriends. I wish girls were attracted to me. I don't know why they aren't."
The 141-page "manifesto" outlined his plans and talked of how he narrowly evaded being found out when police knocked on his door.
"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 a manifesto obtained by California's KEYT-TV, excerpts of which were published by the Los Angeles Times.
"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. I would have been thrown in jail, denied of the chance to exact revenge on my enemies.
"I can't imagine a hell darker than that. Thankfully, that wasn't the case, but it was so close," he wrote.
"The police interrogated me outside for a few minutes, asking me if I had suicidal thoughts. I tactfully told them that it was all a misunderstanding, and they finally left," he added.
"For a few horrible seconds I thought it was all over. When they left, the biggest wave of relief swept over me. It was so scary," he said in the manifesto, according to the newspaper.
Mr Brown said the video was "obviously the work of a madman", adding: "It is very, very apparent that he was severely mentally disturbed."
He revealed that the three guns found in Rodger's car - two Sig Sauer P226 handguns and a Glock 34 Long Slide - were legally bought from licensed firearms dealers and were registered in his name.
Mr Brown revealed officers had come into contact with Rodger three times over the last year, including in January when he performed a citizen's arrest on his room-mate for stealing a candle, and last month when Rodger's family asked police to check on him after they were concerned for his welfare.
He said officers found him "polite and courteous" and saw no reason to detain him on mental health grounds. He said he refused to "second guess" his officers' decision.
Among the victims was 20-year-old student Christopher Michael-Martinez, who was shot dead inside a deli. His room-mate tried to revive him but he died at the scene.
His father Richard Martinez, who spoke with his son 45 minutes before he died, told reporters: "Our family has a message for every parent out there - you don't think it will happen to your child until it does.
"Chris was a really great kid, ask anyone who knew him. His death has left our family lost and broken.
"Why did Chris die? Chris died because of craven, irresponsible politicians and the NRA (National Rifle Association). They talk about gun rights, what about Chris's right to live?
"When will this insanity stop? When will enough people say, 'Stop this madness, we don't have to live like this'. Too many have died. We should say to ourselves, 'Not one more'."
Witness Alexander Mattera, 23, said: "We heard so many gunshots, it was unbelievable. I thought they were firecrackers. There had to have been at least, like, two guns. There were a lot of shots."
Mr Shifman said Rodger had received help from "multiple therapists", and added his social worker was sufficiently concerned about him to call the police last week.
He said it was a tragedy of "immense consequences" and that the Rodger family was co-operating fully with police.
Mr Shifman said: "My client's mission in life will be to try to prevent any such tragedies from ever happening again. This country, this world, needs to address mental illness and the ramifications from not recognising these illnesses."
He added that the family was "staunchly against guns" and supported gun-control laws. "They are extremely, extremely upset that anybody was hurt under these circumstances," he said.
The sister of Peter Rodger, who was an assistant director on The Hunger Games, told Sky News the family was "in total shock" and she condemned US gun laws.
Jenni Rodger, who lives in Cazals, France, said: "I can't imagine how awful this must be for the families of those killed. My heart goes out to them.
"I don't know how on earth a sick, disturbed young man was able to get hold of a gun.
"He was always a disturbed child. I don't know how he was allowed to get a gun. Something has to be done about gun laws in America."
She added: "Pete is absolutely broken. He is such a sensitive being. I can't see how he'll ever recover from this."
A surveillance camera captured the shooting in the I.V Deli in Isla Vista, where Mr Martinez was killed.
The video, obtained by CNN, shows customers queuing at the cash register before they duck to the floor and a glass door shatters as shots are fired from outside the shop.
The news network said the video also shows the moment Mr Martinez runs inside and is hit twice by bullets before his friends perform CPR, but that part of the video was not broadcast.
From the deli the gunman drove to a nearby apartment complex where witness Ellen Cotton recorded the gunfire on her phone.
She told the news channel: "It was horrible and sad. I am still in shock that it happened here, it was so random."