What was going on inside the mind of Elliot Rodger, the young man who killed six people, Santa Barbara, California?
One survivor of the rampage who was shot five times outside her sorority house tells ABC News she will never forget Rodger's smirk - just before he opened fire, killing two of her friends.
"I see his face, he smiles at me and then he starts shooting," she said. "He was just he wanted to do this, he looked happy about it."
The Santa Barbara County Sheriff's Department is facing questions about whether they missed an opportunity to stop the rampage.
Police were aware of Rodger's disturbing videos when they spoke to him last month during a welfare check.
But as Sara Sidner reports, they never watched the videos.
"Shy, timid and polite."
That's how Santa Barbara County Sheriff's Department officials describe Elliot Rodger when they made a welfare check on him.
He's the 22-year-old who murdered six people nearly a week ago.
When they questioned him about the disturbing videos his parents had found, Rodgers told them he was having trouble fitting in socially and the videos were merely a way of expressing himself.
A family friend tells CNN his parents tried to get him help - and it was a never-ending battle.
"As soon as you met him he was unbearably reserved, self-contained. He seemed to merge into the walls," the friend said. "I know that he was in therapy, I knew that he was meeting experts, just to get better, really, but he was so distant."
It's a story heard before: young middle-class men, in need of help, committing mass murder.
Why is that?
Ted Rowlands has this OutFront Investigation.
What motivates someone like Santa Barbara college student Elliot Rodger to kill?
Rodger is just one of many troubled young people who commit heinous crimes.
But can kids who kill actually be rehabilitated?
Jean Casarez has this OutFront investigation on the minds of killer teens.
Chris Martinez was the final victim Elliot Rodger killed in a rampage Friday night near the University of California, Santa Barbara, police said.
The violence came to an end when Rodger died, apparently from a self-inflicted gunshot wound, authorities said.
Investigators say Rodger's murder rampage was a twisted attempt to get revenge against a world he felt rejected him.
His frustrations were detailed in YouTube videos and a 137 page manifesto.
Martinez's father is pushing for a national conversation about mental health and guns.
CNN's Kyung Lah has the story.