ISLA VISTA, Calif. -- The man who murdered six college students in Santa Barbara, California, did not hide his hatred of women.
His angry threats were posted online -- for all the world to see.
So why wasn't he stopped?
Elliot Rodger's Internet videos became darker in February. Police did not become aware of them until alerted by his family.
"Law enforcement does not routinely monitor social media unless there is some authorized law enforcement purpose," said Shawn Henry, a former executive assistant director of the FBI and president of cyber security firm CrowdStrike.
"What they've got to do is actually look for some indication that somebody has committed a crime, is going to commit a crime, they're launching a particular threat against an individual or group of individuals, in which case law enforcement can take specific actions," he said.
The earlier videos were angry but vague. His YouTube message Friday was specific: "I'll take to the streets of Isla Vista and slay every single person I see there."
YouTube prohibits video that threatens "serious acts of violence" or promotes "hatred against individuals or groups."
But it's largely left up to YouTube users to flag videos that the company may then remove.
Jack Lerner studies Internet law and policy at the University of Southern California.
"Over 100 hours of content per minute gets uploaded to YouTube that it's almost impossible to stop something from being online if somebody wants to put online," he said.
In his video, Rodger said, "If I can't have you, girls, I will destroy you."
Rodger's rants against women inspired more than 1.5 million Twitter users to post messages against sexism using the hashtag YesAllWomen. They include:
"#YesAllWomen because I can't walk my dog in my own neighborhood without getting cat called by grown men."
"#YesAllWomen because I have to walk around with a key blade in my hand to feel safe."
The YesAllWomen hastage has now spread all around the world. You're seeing women in Pakistan and Indonesia tweeting about their experiences with harassment and fear. And we should mention that some men are using it too, mainly in support of women.