BIG BEAR LAKE, Calif. » Law enforcement officers working in falling snow and freezing temperatures searched a Southern California mountain today for the former Los Angeles police officer accused of carrying out a killing spree because he felt he was unfairly fired from his job.

“We’re going to continue searching until either we discover that he left the mountain or we find him, one of the two,” San Bernardino County Sheriff John McMahon said at a midmorning news conference.  

More than 100 officers from various agencies were searching for Christopher Dorner in the Big Bear Lake region of the San Bernardino Mountains east of Los Angeles.

Deputies were driven up snowbound roads on Snowcat tractors and armored personnel carriers equipped with snow chains, he said, but helicopters were grounded because of the storm.

A search of dozens of homes in the Big Bear community failed to find Dorner and the search was concentrating farther back in the mountains, near and above the place where his burnt-out pickup truck was found on Thursday, the sheriff said.

Officers followed what appeared to be Dorner’s tracks from the truck but lost them on the frozen ground, McMahon said.

“There’s a lot of cabins up there that are abandoned. We want to make sure that he didn’t find a place to hide out for the night,” he said.

A couple of reported sightings of Dorner didn’t pan out and “we have no information that he’s come down into the community at all,” McMahon said.

Local ski areas were open, but Bear Valley schoolchildren had the day off because of the manhunt.

About 150 miles to the south, up to 16 San Diego County sheriff’s deputies spent the night surrounding and searching a rural home after a hoaxer reported Dorner was there. There were people at home but Dorner wasn’t one of them, said Lt. Jason Rothlein. Investigators have a pretty good idea who made the call and will seek criminal charges, he said.

Though the focus is on the resort area, the search for Dorner, 33, stretches across California, Nevada, Arizona and northern Mexico. LAPD officers are especially on edge because Dorner, who was fired from the force in 2008 after three years on the job, promised in rambling writings to bring “warfare” to police and their families.

Authorities conceded that the whereabouts of Dorner, also a former Naval reservist and onetime college running back, remained a mystery.

The saga began Sunday night, when Monica Quan, the daughter of a former Los Angeles police captain, and fiance Keith Lawrence were found shot in their car at a parking structure at their condominium in Irvine. Quan was an assistant women’s basketball coach at Cal State Fullerton.

The following morning in National City, near San Diego, some of Dorner’s belongings, including police equipment and paperwork with names related to the LAPD, were found in a trash bin.

The LAPD was notified of the find, and two days later informed Irvine police of an angry manifesto written by a former officer and posted on Facebook. Among those named as targets was Quan’s father, Randal Quan, the former LAPD captain who became an attorney who represented Dorner in his unsuccessful attempts to keep the police job he lost in 2008 for making false statements.

“Bing bing bing, the dots were connecting,” Irvine police Lt. Julia Engen said. “These names are somehow associated to Mr. Quan, who just lost his daughter the prior day. The dots connected. OK, now we’ve got a name of somebody to look at. That’s when the discovery was connected.”

On Wednesday night, Irvine and Los Angeles police announced they were searching for Dorner, declaring him armed and “extremely dangerous.” Hours later, they learned they were all too correct.

Two LAPD officers en route to provide security to one of Dorner’s possible targets were flagged down by a resident who reported seeing the suspect early Thursday at a gas station in Corona. The officers then followed a pickup truck until it stopped. The driver, believed to be Dorner, got out and fired a rifle, police said. A bullet grazed an officer’s head.

Later, two officers on routine patrol in neighboring Riverside were ambushed at a stoplight 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.

Thousands of heavily armed officers patrolled highways throughout Southern California, while some stood guard outside the homes of people police said Dorner vowed to attack. Electronic billboards, which usually alert motorists about the commute, urged them to call 911 if they saw him.

At a news conference held amid heightened security in an underground room at police headquarters, Los Angeles Police Chief Charlie Beck urged Dorner to surrender.

“Of course he knows what he’s doing; we trained him. He was also a member of the Armed Forces,” he said. “It is extremely worrisome and scary.”

While in the Naval Reserves, Dorner earned a rifle marksman ribbon and pistol expert medal. He was assigned to a naval undersea warfare unit and various aviation training units, according to military records, taking a leave from the LAPD to be deployed to Bahrain in 2006 and 2007.

He wrote that he would “utilize every bit of small arms training, demolition, ordinance and survival training I’ve been given,” the manifesto read.

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

LAPD officers guarding a target named in the manifesto shot and wounded two women in suburban Torrance who were in a pickup truck delivering newspapers. Investigators said Maggie Carranza, 47, and her mother, Emma Hernandez, 71, were in a Toyota Tundra, similar to Dorner’s Nissan Titan. Carranza had minor hand injuries. Hernandez was hospitalized with a gunshot wound in the back. A lawyer said they had no warning.

Minutes later, Torrance officers responding to a report of gunshots encountered a dark pickup matching the description of Dorner’s, police said. 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, they said.

In San Diego, where police said Dorner 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.

Navy Cmdr. Brad Fagan said officials believe Dorner had checked into a base hotel on Tuesday and left the next day without checking out. Numerous agencies guarded the base on Thursday. Fagan said Dorner was honorably discharged and that his last day in the Navy was last Friday.

Nevada authorities also joined the search, because Dorner owns a house nine miles from the Las Vegas Strip.

And agents were inspecting a package sent to CNN’s Anderson Cooper that arrived in New York on Feb. 1, days before the first two killings. It contained a note on it that read, in part, “I never lied.” A coin typically given out as a souvenir by the police chief was also in the package, riddled with bullet holes.

Dorner’s writings suggested he did not expect to live through the ordeal.

“Unfortunately, I will not be alive to see my name cleared,” he wrote at one point in his manifesto, later saying, “Self-preservation is no longer important to me. I do not fear death as I died long ago.”

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Associated Press writers contributing to this report include Jeff Wilson, Bob Jablon, Greg Risling, Shaya Tayefe Mohajer, Linda Deutsch and John Antczak in Los Angeles, Ken Ritter in Las Vegas, and Elliot Spagat and Julie Watson in San Diego.