The plot may have been years in the making, but the killer gave just minutes' notice before he rained terror across a Southern California community.
Now, shattered glass and flowers mark the path of horror created by a young man bent on getting his revenge for perceived slights and chronic problems with women.
In the three days since the rampage that left six people and the assailant dead, a slew of new information has emerged about the victims, the suspect and what led up to the stabbings and shootings.
Here's what we know:
The rampage started with his roommates
Authorities now know Elliot Rodger's killing spree across Isla Vista began before he even left home.
The 22-year-old former Santa Barbara City College student fatally stabbed three young men in his own apartment -- George Chen, 19, Cheng Yuan Hong, 20, and Weihan Wang, 20.
Chen and Hong were the attacker's roommates.
A friend of Rodger's family said Rodger recently had a feud with his roommates, complaining to his landlord that his roommates were too noisy and played lots of video games.
The assailant himself outlined his plan to kill two roommates in a 137-page manifesto he left behind.
"I'd even enjoy stabbing them both to death while they slept," Rodger wrote.
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The assailant had been seeing therapists
Rodger's history of mental health issues was no secret to his family, and the young man was seeing at least two therapists prior to his death.
He had been seeing therapists on and off since he was 8, family friend Simon Astaire said. When he went to high school in Van Nuys, California, he met with a therapist "pretty much every day," Astaire said.
Rodger's family contacted police after discovering social media posts about suicide and killing people, family spokesman and attorney Alan Shifman told reporters Saturday.
Six policemen showed up at Rodger's home in Isla Vista on April 30, but they found nothing alarming. So they told Rodger to call his mother and they reassured her that he was OK, according to Astaire.
Santa Barbara County Sheriff Bill Brown told reporters Saturday that at the time, deputies "determined he did not meet the criteria for an involuntary hold."
Brown said Rodger told deputies it was a misunderstanding and that he was not going to hurt anyone or himself. Rodger said he was having troubles with his social life.
But long before that, Rodger was plotting his deadly "Day of Retribution."
"I had the striking and devastating fear that someone had somehow discovered what I was planning to do, and reported me for it," Rodger wrote about the police visit, toward the end of his manifesto. "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."
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He sent his manifesto to two dozen people
Perhaps some of the most obvious clues as to why the rampage took place come from Rodger's manifesto, which chronicles his life from birth all the way to his planned "Day of Retribution."
In "My Twisted World: The Story of Elliot Rodger," the writer said he bought his first handgun in 2012 in preparation for a possible "Day of Retribution."
On Friday, minutes before he shot three young women in front of a sorority house and killed a young man at a nearby deli, Rodger e-mailed his writings to two dozen people, including his parents and at least one of his therapists.
"My orchestration of the Day of Retribution is my attempt to do everything, in my power, to destroy everything I cannot have," Rodger wrote.
"All of those beautiful girls I've desired so much in my life, but can never have because they despise and loathe me, I will destroy. All of those popular people who live hedonistic lives of pleasure, I will destroy, because they never accepted me as one of them. I will kill them all and make them suffer, just as they have made me suffer. It is only fair."
One of the people he mentioned by name in the manifesto is Lucky Radley, a childhood friend, who he said became "an object of my extreme jealousy and hatred."
"When I saw that, I was shocked," Radley told CNN's "New Day" on Monday. "I literally didn't believe that was coming from him."
Radley said Rodger was an abnormally quiet boy who barely spoke, even when Radley went to Rodger's house a couple of times to play.
He hadn't seen Rodger since high school. Seeing Rodger's video now, Radley told CNN, "That's the first time me hearing him say more than a one-word answer."
Rodger's mother, Lichin, saw the e-mailed manifesto at 9:17 p.m. Friday. She went to Rodger's YouTube page and saw a disturbing video in which her son talked about "slaughtering" women at a sorority house at the University of California at Santa Barbara, Astaire said.
His mother called 911 and Rodger's father, and the parents left Los Angeles, headed for Santa Barbara, the family friend said. En route, they heard there was a shooting. Later that night, they found out their son was the gunman.
All the deceased victims were UCSB students
Chen, Hong and Wang, the three men fatally stabbed in Rodger's apartment, were students at the University of California, Santa Barbara -- as were the three other victims who didn't survive.
UCSB canceled classes until Wednesday and declared Tuesday to be a day of mourning, with a memorial service set for Tuesday afternoon. Counselors are available on campus for anyone needing support, the university said.
The two young women fatally shot outside the Alpha Phi sorority house -- Katherine Cooper, 22, and Veronika Weiss, 19 -- were members of the Delta Delta Delta sorority at UCSB.
"Katie will be remembered for her generous spirit and warm heart. Veronika will be remembered for her vibrant personality and enthusiasm for life," Delta Delta Delta President Phyllis Durbin Grissom wrote.
The sixth victim killed was Christopher Martinez, who was getting a sandwich at a deli when he was shot. The 20-year-old UCSB student was known for his selflessness.
"Chris was just an amazing guy," Jeff Dolphin, Martinez's freshman-year roommate, told the Los Angeles Times.
"If I was going through something, he was always there for me. If I needed something, he was there. If I needed a textbook, if I was locked out of the room because I forgot my key, he would stop playing basketball or doing what he was doing to unlock the door so I didn't have to get charged. He was just a great guy."
Martinez's father, Richard Martinez, lambasted politicians and the National Rifle Association after his son's death. He told CNN's Kyung Lah that nothing has changed since the Sandy Hook Elementary School shootings in 2012, when 20 children and six adults were killed.
"Have we learned nothing? These will continue until somebody does something. Where the hell is the leadership?" Richard Martinez asked.
"He's our only child. And he died on Friday. I'm 61 years old now. I'll never have another child. He's gone."
The community is trying to move forward
While some try to understand why the tragedy happened, others say it's a lost cause.
"I don't need an explanation. It's, unfortunately, a very sad situation that no explanation can ever justify," said Ryan Booth, manager of the I.V. Deli Mart, where Martinez died.
He said he refuses to read the killer's manifesto or watch his YouTube video, "Retribution."
"As a community we have to be strong and stand up and try and move on."