Police are looking for an ex-Los Angeles cop turned suspected cop killer and people are being warned not to answer their doors unless it's someone they know. Some parents say they're scared to send their kids to school.

The LAPD says Christopher Dorner killed three people, including one officer. They say on Sunday in Irvine, Dorner killed a woman and her fiance in their car. She was the daughter of a retired cop who handled Dorner's appeal after he was fired from the force.

Then early Thursday morning, police say he shot and wounded an officer in Corona, about 100 miles away. Twenty minutes later, he allegedly ambushed and shot two officers at a stoplight in Riverside, killing one of them.

Police focused their search for Dorner on a ski town called Big Bear Lake, about 100 miles from Los Angeles. There, authorities found his truck on fire.

Dorner posted an 11-page manifesto online, promising a "war" on police and their families for being fired in 2008. In it he warns, "I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

Police are on edge. There were two cases of officers shooting at innocent bystanders because their trucks look like Dorner's.  In one case, two people were shot while delivering newspapers.