BIG BEAR LAKE, Calif. (AP) -- All that was left were footprints leading away from Christopher Dorner's burned-out pickup truck, and an enormous, snow-covered mountain where he could be hiding among the skiers, cabins and dense woods.
More than 100 officers in glass-enclosed snow machines and armored personnel carriers sought the former Los Angeles police officer suspected of going on a deadly rampage and vowing to go after those on the force who wronged him.
With bloodhounds in tow, officers went door to door as snow fell, aware to the reality that they could be walking into a trap set by the well-trained former Navy reservist who knows their tactics and strategies as well as they do.
"The bad guy is out there, he has a certain time on you, and a distance. How do you close that?" asked T. Gregory Hall, a retired tactical supervisor for a special emergency response team for the Pennsylvania State Police.
"The bottom line is, when he decides that he is going to make a stand, the operators are in great jeopardy," Hall said.
Just as authorities were dispatching officers to the mountain, a growing cadre of heavily armed police spread throughout California, Nevada, Arizona and northern Mexico stayed on the lookout for him.
Police said officers are still guarding more than 40 targets mentioned in a rant they said Dorner posted on Facebook. He vowed to use "every bit of small arms training, demolition, ordinance and survival training I've been given" to bring "warfare" to the LAPD and its families.
Possible sightings were reported near Barstow, at Point Loma base near San Diego, in downtown Los Angeles, leading some law enforcement officials to speculate that he appeared to be everywhere and nowhere, and that he was trying to spread out their resources.
For the time being, their focus was on the mountains 80 miles east of Los Angeles - a snowy wilderness, filled with deep canyons, thick forests and jagged peaks, that creates peril as much for Dorner as the officers hunting him.
After the discovery of his truck Thursday afternoon, SWAT teams in camouflage started scouring the mountains. As officers worked through the night, a storm blew in, possibly covering the trail of tracks that had led them away from his truck.
The small army has the advantage of strength in numbers and access to resources, such as special weapons, to bring him in.
"We're prepared to use our expertise in terms of special weapons and tactics to address any threat that he poses," LAPD Deputy Chief Kirk Albanese said. "We're working with other agencies ... to make sure we take the advantage of our side as much as we can."
In his online rant, Dorner sprinkled in military and police parlance, seemingly baiting authorities.
"Any threat assessments you generate will be useless," it read. "This is simple. I know your TTP's (techniques, tactics, and procedures) and PPR's (pre-planned response). I will mitigate any of your attempts at preservation."
Without the numbers that authorities have, Dorner will likely rely on the element of surprise, experts said.
"He doesn't even have to stand and fight," Hall said. "He makes his shot of opportunity and flees."
It's an advantage that Dorner is well aware of. In his posting, he wrote: "I have the strength and benefits of being unpredictable, unconventional, and unforgiving. Do not waste your time with briefs and tabletops.
"Whatever pre-planned responses you have established for a scenario like me, shelve it," he said.
Authorities said they do not know how long Dorner has been planning the rampage. It's not clear if he has provisions, clothing or weapons stockpiled in the area. Even with training, days of cold and snow can be punishing.
"Unless he is an expert in living in the California mountains in this time of year, he is going to be hurting," said former Navy SEAL Clint Sparks, who now works in tactical training and security. "Cold is a huge stress factor.
"If he is not prepared to wait that out, or he hasn't done it before, not everybody is survivor-man," Sparks said.
Police said they also don't know what exactly set off him.
Dorner served in the Navy, earning 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.
He took leave from the LAPD for a deployment to Bahrain in 2006 and 2007.
Last Friday was his last day with the Navy and also the day CNN's Anderson Cooper received a package that 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.
Police believe that indicates some level of pre planning.
On Sunday, police say he shot a couple in a parking garage at their condominium in Irvine. The woman was the daughter of a retired police captain who had represented Dorner in the disciplinary proceedings that led to his firing.
Dorner wrote in his manifesto that he believed the retired captain had represented the interests of the department over his.
Authorities believe Dorner used a rifle to ambush two Riverside police officers Thursday on routine patrol, killing one and seriously wounding the other. The incident led police to believe he was armed with multiple weapons, including an assault-type rifle.
That detail concerned officers whose bullet-proof vests can be penetrated by such high-powered weapons, Albanese said.
Because of this, all LAPD officers have been required to work in pairs, to ensure "a greater likelihood of coming out on top if there is an ambush," Albanese said. "We have no officers alone right now."
On Friday, law enforcement officials in Big Bear said they will continue to search for Dorner through the weekend. They were also inspecting his truck for clues and were following up on multiple theories, including whether he intentionally left it there.
"Here's the bottom line, we don't know," Albanese said.
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.