Police have located the burned-out vehicle belonging to a former Los Angeles police officer who authorities say is on a lethal mission to punish those he blames for his firing.

The manhunt for Christopher Dorner, who is believed to have killed three people since Sunday night, stretches across three states and into Mexico, stirring fear throughout the region.

Police found Dorner's truck late Thursday afternoon near the Bear Mountain ski area at Big Bear Lake, about 120 kilometres east of Los Angeles. San Bernardino County Sheriff John McMahon said officers were going door to door looking for him.

]Throughout the day, thousands of heavily armed officers patrolled highways in the state. Some stood guard outside the homes of people police say Dorner vowed to attack in an angry rant posted online. Electronic billboards that usually alert motorists to commute times urged them to call 911 if they saw him or his truck

Police issued a statewide "officer safety warning" and police were sent to protect people named in the posting that was believed to be written by the fired officer, Christopher Dorner, who has military training. Among those mentioned were members of the Los Angeles Police Department.

"I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," said the manifesto. 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."

Dorner has available multiple weapons including an assault rifle, said police Chief Charlie Beck, who urged Dorner to surrender. "Nobody else needs to die," he said.

Christopher Dorner, 33, is the subject of a massive police manhunt in southern California. Dorner is accused of three killings, including the shooting death of a police officer. (Los Angeles Police Department/Associated Press)

More than 40 protection details were assigned to Dorner's possible targets. Police spokesman Cmdr. Andrew Smith said he couldn't remember a larger manhunt by the department.

The hunt spread from California to Nevada, Arizona and Mexico, said a U.S. Marshals Service official who spoke to The Associated Press on condition of anonymity because the official was not authorized to publicly comment.

The search for Dorner, who was fired from the LAPD in 2008 for making false statements against a fellow officer, began after he was linked to a weekend killing in which one of the victims was the daughter of a former police captain who had represented him during the disciplinary hearing.

Authorities believe Dorner opened fire early Thursday on police in cities east of Los Angeles, killing an officer and wounding another.

Beck detailed Dorner's alleged crimes in an unusual news conference in an underground room at police headquarters, where extra security had been 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.

Police said Dorner, 33, implicated himself in the couple's killings with the multi-page "manifesto."

A Facebook post believed written by Dorner said he knew he would be vilified by the LAPD and the news media, but that "unfortunately, this is a necessary evil that I do not enjoy but must partake and complete for substantial change to occur within the LAPD and reclaim my name."

"I never had the opportunity to have a family of my own, I'm terminating yours," the posting said.

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

Los Angeles area on edge

The Los Angeles area is on edge. The nearly 10,000-member LAPD has dispatched many of its officers to protect potential targets. The department also pulled officers from motorcycle duty, fearing they would make easy targets.

In San Diego, where Dorner allegedly tied up an elderly man and unsuccessfully tried to steal his boat Wednesday night, Naval Base Point Loma was locked down Thursday after a navy worker reported seeing someone who resembled Dorner.

'Nobody else needs to die.'— Police Chief Charlie Beck

Navy Cmdr. Brad Fagan said officials don't believe he was on base Thursday but had checked into a base hotel on Tuesday and left the next day without checking out. Numerous agencies guarded the base.

Fagan said Dorner was honourably discharged and that his last day in the navy was last Friday.

Nevada authorities also looked for Dorner because he owns a house 15 kilometres from the Las Vegas Strip, according to authorities and court records.

The hunt for Dorner led to two errant shootings in the pre-dawn darkness Thursday.

Los Angeles officers guarding a "target" named in the posting shot and wounded two women in suburban Torrance who were in a pickup but were not involved, authorities said. Beck said one woman was in stable condition with two gunshot wounds and the other was being released after treatment.

"Tragically we believe this was a case of mistaken identity by the officers," Beck said.

Minutes later Torrance officers responding to a report of gunshots encountered a dark pickup matching the description of Dorner's, said Torrance Sgt. Chris Roosen. A collision occurred and the officers fired on the pickup. The unidentified driver was not hit and it turned out not to be the suspect vehicle, Roosen said.

"We're asking our officers to be extraordinarily cautious, just as we're asking the public to be extraordinarily cautious with this guy. He's already demonstrated he has a propensity for shooting innocent people," said Smith, the LAPD commander.

Couple shot to death

Dorner is wanted in the killings of Monica Quan and her fiancé, 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.

Law enforcement officials arrive at the scene of a shooting in Torrance, Calif., where police opened fire on a vehicle they thought was driven by Christopher Dorner. (Chris Carlson/AP)

Dorner was with the department from 2005 until 2008, when he was fired for making false statements.

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, LAPD Capt. William Hayes told The Associated Press Wednesday night.

Randal Quan retired in 2002. He later served as chief of police at Cal Poly Pomona before he started practising law.

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 whether "he had been in a fight because his face was puffy," and his son responded that he had been kicked twice in the chest by a police officer.

Early Thursday, the first shooting occurred in Corona and involved two LAPD officers working a security detail, said LAPD Sgt. Alex Baez. A citizen pointed out Dorner to the officers who followed until his pickup stopped and the driver got out and fired a rifle at them, officials said, grazing one officer's head.

Later, two officers on routine patrol in neighbouring Riverside were ambushed at a stop light by a motorist 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, said Riverside police Chief Sergio Diaz.

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