A 137-page memoir details the jealousy and anger Elliot Rodger felt before he killed six people in a furious rampage near the University of California, Santa Barbara.
"All I ever wanted was to fit in and live a happy life amongst humanity, but I was cast out and rejected, forced to endure an existence of loneliness and insignificance, all because the females of the human species were incapable of seeing the value in me," he wrote in the document, titled "My Twisted World."
Police identified Rodger, 22, as the shooter, a man who videotaped his rage over his rejection by women and vowed "retribution" just hours before the killing began. He was also identified as the killer by a lawyer for his father Peter Rodger, who was the assistant director for one of the “Hunger Games” films.
Read: Father of Santa Barbara Victim Sobs and Rails Against Son’s Death
In the manifesto, Rodger described police visiting him after he uploaded several videos to YouTube. A member of his family asked police to check on him because of alarm over his behavior and videos.
"As soon as I saw those cops, the biggest fear I had ever felt in my life overcame me," he wrote. "I had the striking and devastating fear that someone had somehow discovered what I was planning to do, and reported me for it."
In a YouTube video titled "Elliot Rodger's Retribution" that he posted before the killing spree began, Rodger sat in the driver's seat of a car as he promised "retribution" and discussed his "loneliness, rejection and unfulfilled desires."
"Girls gave their affection and sex and love to other men but never to me," he said in the video, which he added would be his last.
Rodger also expressed the jealousy he felt toward his younger brother, who he described as socially savvy.
"It is very unfair how some boys are able to live such pleasurable lives while I never had any taste of it, and now it has been confirmed to me that my little brother will become one of them," Rodger wrote in the manifesto. "He will become a popular kid who gets all the girls. Girls will love him. He will become one of my enemies."
Santa Barbara County Sheriff Bill Brown called the manifesto "rambling."
Friend Calls Rodger "a Really Lonely Guy"
Andi Chan, a friend of Rodger for two and a half years, described him as a "really lonely guy" who was often depressing to be around.
"Me and my friends tried to help him," said Chan. "He doesn't like to talk or hang out."
Chan said Rodger often talked about finding a girlfriend, something he echoed in videos posted to YouTube and the manifesto.
"He asked why the world is unfair to him. 'I'm a good looking guy. Why do girls like ugly, fat guys?'" said Chan. "I told him appearance wasn't everything."
Chan said after they saw the 2012 film "Chronicle," Rodger said he wanted to "dominate the world." In the film, three high school students gain superpowers and one character - who's bullied, shy and lonely - eventually uses them in a robbery and in an attempt to kill his father. He dies at the end of the film, killed by one of the other students.
"We all thought he was insane but we were used to it," said Chan. "Maybe in his mind he really wanted to do that."
Chan said he realized Rodger was involved in the shooting when he saw a photo of his BMW.
"I started to search for the shooter's name, then I saw stuff on Facebook," he said. "I was shocked and disappointed. No matter how angry you get, you are - you can't kill people."
Families, Sorority Mourn Victims of Santa Barbara Killings
Police identified three of the victims - 22-year-old Katherine Breann, 19-year-old Veronika Weiss and 20-year-old Christopher Michaels-Martinez. The other three victims haven't been identified.
Four of the injured were treated and released from Goleta Valley Cottage Hospital, according to Dr. Stephen Kaminski, the director of trauma services at the hospital.
Six others remain at Santa Barbara Cottage Hospital, where three are in good condition, one is in fair condition and two are in serious condition, said Kaminski. A seventh victim was released.
Two of the victims were members of the sorority Delta Delta Delta, which issued a statement Saturday saying: "Tri Delta is devastated to learn of the tragic event at the University of California, Santa Barbara and so very saddened to learn of the death of two of our members. Our hearts go out to their families and our sisters at Gamma Theta. Tri Delta's staff, volunteers and local alumnae are working with the chapter to provide support as they grieve this loss."
The University of California, Santa Barbara, also issued a statement, saying in part: "Our campus community is shocked and saddened by the events that occurred last night in the nearby community of Isla Vista. Our thoughts and prayers are with the victims and their families who are grieving and mourning as a result of this tragedy."
Rodger's Murderous Spree
Rodger's began the spree by stabbing to death three people in his home Friday, police said. He then drove around the Isla Vista neighborhood, killing three others and injuring 13 more.
The murderous spree ended when he crashed his car with a bicyclist he had struck on his car windshield. He was found with a gunshot to his head.
"It would appear he took his own life," said Brown.
Police said three guns were recovered from Rodger's car. Police said he had more than 400 rounds of ammunition.
"All were legally purchased from federally licensed dealers and all were registered to the suspect," said Brown. "It's been difficult really on all of us in terms of the tragic nature that has occurred here."
Concerns Over Rodger's Well Being Reported
Brown said police have had three previous contacts with Rodger before Friday's shooting.
One of the other incidents occurred in January when he made a citizen's arrest of his roommate for allegedly stealing three candles, and again in July 2013 when he claimed he had been assaulted. Police determined that Rodger may have been the aggressor, Brown said.
Rodger was being treated by multiple therapists and was a student at Santa Barbara City College, said family lawyer Alan Schifman.
Schifman said in recent weeks that Rodger’s parents were concerned for their son's well being and reported his disturbing YouTube videos to police, which lead to an investigation. According to Schifman, police interviewed Rodger on April 30 and found him to be “polite and kind.” He did not specify which law enforcement division conducted the interview.
Brown said the officers found no reason to take further action on Rodger.
"Someone has to exhibit that they are a danger to themselves or other people to be committed under California law," said Brown. “He (Rodger) presented himself in a manner that convinced them that he was not a danger to himself or other people.”
A social worker also contacted police about Rodger last week, said Schifman.
Schifman said Rodger was diagnosed as being a high-functioning patient with Asperger syndrome and had trouble making friends.
Brown said Rodger at one time was prescribed medication that he didn't take.
"I think what we need to do is to do a better job as a society of identifying mental illness," said Brown.
ABC News consultant and former FBI special agent Brad Garrett said authorities are often asked to be both law enforcers and psychiatric social workers.
"When they are given a set of facts, they take them," said Garrett. "It would appear that they sort of put it to rest at that point and felt like what else can we really do?"