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A truck found abandoned and burning near a Southern California ski area belonged to a fugitive former Los Angeles police officer suspected in three murders, authorities confirmed Thursday afternoon, as thousands of officers searched for the suspect across three states and into Mexico.

The suspect has been identified as Christopher Jordan Dorner, 33, and he is considered extremely dangerous and armed with multiple weapons, authorities say. He is accused of killing a college basketball coach and her fiance last weekend, then following through on a vow to kill police by opening fire Wednesday night on three officers, killing one.

The killings appear to be retaliation for his 2008 termination from the Los Angeles Police Department for making false statements, authorities say. Dorner posted an online manifesto that warned, "I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

It also asserted: "Unfortunately, I will not be alive to see my name cleared. That's what this is about, my name. A man is nothing without his name."

Los Angeles police believe the manifesto posted to Facebook was written by Dorner because there are details in it only he would know.

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"In this case, we're his target," Sgt. Rudy Lopez from the Corona Police Department told reporters Thursday morning after an attack on the department's officers.

Dorner's pickup truck was found burned out near the Big Bear ski area Thursday morning about 80 miles east of Los Angeles. A 10-man tactical team arrived to search the surrounding area. Several Big Bear schools were put on lock-down, and the ski resort closed its slopes, as FBI agents manned a checkpoint to question drivers leaving the area.

San Bernardino County Sheriff John McMahon said 125 officers were going door to door and attempting to track the suspect, and that a SWAT team was providing added security to those in the community.

"Certainly he could be anywhere at this point. That's why were searching door to door," McMahon said.

A U.S. Marshals Service official says the search for Dorner has expanded from California to Nevada, Arizona and Mexico.

The massive manhunt began after Dorner was linked to a weekend killing, in which one of the victims was the daughter of a former police captain who had represented Dorner during his disciplinary hearing. Authorities think Dorner followed up that attack by opening fire late Wednesday on police in cities east of Los Angeles, killing an officer and wounding another.

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"Nobody else needs to die," Los Angeles Police Chief Charlie Beck said urging Dorner to surrender. "Of course he knows what he's doing, we trained him. He was also a member of the armed forces. It is extremely worrisome and scary."

Beck detailed Dorner's alleged crimes in an unusual press conference in an underground room at police headquarters, where extra security was deployed. The chief said there had been a "night of extreme tragedy in the Los Angeles area" and that all measures were being implemented to ensure officer safety.

Adding to the mystery, CNN personality Anderson Cooper tweeted Thursday that he had received a package from Dorner that purportedly contained "a note, DVD and a coin shot thru with bullet holes."

Dorner served in Iraq, providing security on an oil platform and has received awards including the Rifle Marksman Ribbon and a Pistol Expert Medal, among others. Based on his awards and deployment records, the Navy told FoxNews.com that Dorner would not be classified as an advanced shooter.

Dorner is wanted in the killings of Monica Quan and her fiance, Keith Lawrence. They were found shot in their car at a parking structure at their condominium on Sunday night in Irvine, authorities said. Quan, 28, was an assistant women's basketball coach at Cal State Fullerton. Lawrence, 27, was a public safety officer at the University of Southern California.

Quan's father, a former LAPD captain who became a lawyer in retirement, represented Dorner in front of the Board of Rights, a tribunal that ruled against Dorner at the time of his dismissal.

According to documents from a court of appeals hearing in October 2011, Dorner was fired from the LAPD after he made a complaint against his field training officer, Sgt. Teresa Evans. Dorner said that in the course of an arrest, Evans kicked suspect Christopher Gettler, a schizophrenic with severe dementia.

Richard Gettler, the schizophrenic man's father, gave testimony that supported Dorner's claim. After his son was returned on July 28, 2007, Richard Gettler asked "if he had been in a fight because his face was puffy," and his son responded that he was kicked twice in the chest by a police officer.

The first attack on officers occurred early Thursday in Corona and involved two LAPD officers working a security detail, Los Angeles Sgt. Alex Baez said. A citizen pointed out Dorner to the officers, who followed him until his pickup stopped and he got out, allegedly fired a rifle at them, officials said. One officer's head was grazed by a bullet.

Later, two officers on routine patrol in neighboring Riverside were ambushed at a stoplight by a motorist, suspected to have been Dorner, who drove up next to them and opened fire with a rifle. One died and the other was seriously wounded but was expected to survive, Riverside Police Chief Sergio Diaz said.

Diaz said news organizations should withhold the officers' names because the suspect had made clear that he considers police and their families "fair game."

Dorner's LAPD badge and an ID were found near San Diego's airport and were turned in to police at early Thursday, San Diego police Sgt. Ray Battrick said.

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The Associated Press contributed to this report.