Big Bear Lake, California (CNN) -- Arguably the most wanted man in America, fired police officer Christopher Jordan Dorner may well be in hiding -- plotting his next move after allegedly killing three people. Officers toting high-powered weapons fanned out Friday across Southern California, searching for their former colleague.

More than 100 officers zeroed in on a mountain resort town east of Los Angeles where searchers Thursday found Dorner's burned-out pickup truck.

The manhunt for an ex-cop who's allegedly declared war on police unfolded in a wintry setting, with officers bundled head-to-toe in snowgear as they held the trigger guard on their assault-style rifles.

A storm dropped two inches of snow, forcing motorists to use tire chains, and up to six more inches were expected Friday. The snow, however, was regarded as helpful to police because tracking would be easier, authorities said.

Using snowcat vehicles and dogs, officers were scouring eight square miles in the mountains and were doing one-by-one checks on 200 vacant cabins.

Despite the dragnet, authorities allowed nearby ski resorts to remain open Friday because they don't believe Dorner is in Big Bear Lake, where police already conducted a door-to-door search.

Mayor Jay Obernolte described the day as "a beautiful winter morning." Residents weren't fearful, he said, adding that "many of the people here are armed."

"Is there panic in our community?" Obernolte told reporters. "No, there is no panic.

"We're a hardy people in the San Bernardino Mountains," he added.

As of early Friday afternoon, officers hadn't yet found Dorner, authorities said.

San Bernardino County Sheriff John McMahon said the snowfall slowed some searching done by foot, but police pushed onward, reporting no problems in reaching places.

"The snow is great for tracking folks, as well as looking at each individual cabin to see if there's any sign of forced entry," McMahon said.

"We're going to continue searching until we either discover he left the mountain or we find him," he added. "It's extremely dangerous."

Meanwhile, the county jail in downtown Los Angeles was in lockdown Friday as a precaution after a civilian female employee of the Twin Towers Correctional Facility spotted someone fitting Dorner's description, said sheriff's spokesman Steve Whitmore.

Elsewhere, U.S. Navy installations throughout California and Nevada were "maintaining a heightened security posture," a U.S. military official told CNN.

"Security personnel are on the lookout" for Dorner, the official said. The measure was ordered overnight by Rear Adm. Dixon Smith, commander of the Navy's southwest region.

The official declined to discuss security procedures, but said the move was made after it became clear that Dorner earlier this week was able to get access to the Naval Base at Point Loma and stay in a motel there.

Two sailors reported that he approached them Wednesday and spoke with them for about 10 minutes. The conversation took place at a coastal "riverine" unit in San Diego where Dorner served in 2006. As a Navy reservist, Dorner held security jobs with that unit.

The Navy is not certain whether Dorner still possesses any military identification he might try to use to access a facility. The official confirmed an investigation is under way to determine what military identification he still might have.

Dorner had limited flight training in 2009 at Naval Air Station Fallon in Nevada before serving in San Diego.

In the California mountains, SWAT teams took to snowcats and sped up the mountain while other officers prowled forest roads in an armored personnel carrier. They were searching for Dorner among dozens of abandoned and empty cabins dotting the mountainside above the town. Schools in the community shut down amid the tension.

The 270-pound former Navy lieutenant promised to bring "unconventional and asymmetrical warfare" to police officers and their families, calling it the "last resort" to clear his name and get back at a department that he claims mistreated him.

Dorner, 33, is wanted in the killing of two people in Irvine, California, on Sunday and in the shooting of three Los Angeles-area police officers Thursday, one of whom died.

One of the victims of the Irvine killings, Monica Quan, was the daughter of the retired police officer who represented Dorner in his efforts to get his job back, police have confirmed.

Despite the killings, Dorner seemed to be getting some sympathy. Where police see a violent killer, others saw Dorner as kind of an epic anti-hero waging war against an institution they see as corrupt.

"God bless you Chris #Dorner," one Twitter user posted. "I believe in what goes around comes around. The LAPD is crooked."

Another tweeter said Dorner was wrong, but the "#LAPD has done much worse things than he has."

"My opinion of the suspect is unprintable," Riverside police Chief Sergio Diaz said, hours after one of his officers was killed. "The manifesto, I think, speaks for itself (as) evidence of a depraved and abandoned mind and heart."

Here's what is known so far:

-- Dorner, who worked as a Los Angeles Police Department officer from 2005 to 2008, is accused of killing Quan and her fiance Sunday in Irvine, then shooting two Riverside police officers and an LAPD officer Thursday. Police say he unleashed numerous rounds at the Riverside officers, riddling their car with bullets and killing a 34-year-old officer. The second officer in the car was seriously wounded, and the LAPD officer suffered only minor injuries, police said.

-- In a lengthy letter provided by police, Dorner said he had been unfairly fired by the LAPD after reporting another officer for police brutality. He decried what he called a continuing culture of racism and violence within the department, and called attacks on police and their families "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."

-- Leads have taken police from Los Angeles to San Diego to Las Vegas to the California mountain resort town of Big Bear Lake, where police found Dorner's widely sought gray pickup, thoroughly burned. Despite door-to-door searches and a constant presence since Thursday, police had found no trace of him Friday, McMahon said. Trackers lost footprints believed to be Dorner's in a wooded area near the truck. Investigators turned up no additional evidence that he had either left the area or remained, he said.

-- The LAPD and other agencies have gone to extremes to protect officers. Forty teams of officers were guarding people named as targets in Dorner's letter. On Thursday, one of the teams shot at a pickup that resembled Dorner's but turned out to be a Los Angeles Times newspaper delivery vehicle.

-- Despite Dorner's statement in the letter that "when the truth comes out, the killing stops," Los Angeles police Chief Charlie Beck said authorities don't plan to apologize to Dorner or clear his name. Dorner's firing, Beck said Thursday, had already been "thoroughly reviewed."

-- In Nevada on Thursday, FBI agents searched Dorner's Las Vegas home. The search forced some of Dorner's neighbors out of their homes for several hours, CNN affiliate KLAS reported.

"It's too close to home. It's kind of scary," neighbor Dan Gomez told KLAS.

A message to the media

In addition to posting his manifesto online, Dorner reached out directly to CNN, mailing a parcel to AC360 anchor Anderson Cooper's office at CNN in New York.

The package arrived on February 1 and was opened by Cooper's assistant. Inside was a hand-labeled DVD, accompanied by a yellow Post-it note reading, in part, "I never lied" -- apparently in reference to his 2008 dismissal from the LAPD.

The package also contained a coin wrapped in duct tape. The tape bears the handwritten inscription: "Thanks, but no thanks, Will Bratton." It also had letters that may be read as "IMOA," which could be a commonly used Internet abbreviation for "Imagine a More Open America," or possibly "1 MOA," which means one minute of angle, perhaps implying Dorner was notably accurate with a firearm.

The coin is a souvenir medallion from former LAPD Chief William Bratton, of a type often given out as keepsakes. This one, though, was shot through with bullet holes: three bullet holes to the center and one that nicked off the top.

The editorial staff of AC360 and CNN management were made aware of the package Thursday. Upon learning of its existence, they alerted Bratton and law enforcement.

Bratton headed the LAPD at the time Dorner was dismissed.
Search For Former LA Cop Focuses On Mountain Resort