Trail of fugitive ex-cop turns very cold in Big Bear The massive dragnet for a fugitive ex-cop continued Friday, with more than 100 officers conducting a fruitless search in the snowy, forested mountains around Big Bear Lake for an armed gunman who police say is on a vengeful rampage. As the falling snow piled up, authorities pledged to continue the manhunt until they find Christopher Jordan Dorner, the 33-year-old former Los Angeles police officer suspected of killing three people, or stumble on definitive evidence that he is no longer in the area. The trail has gone cold since Dorner's Nissan Titan pickup was found Thursday morning engulfed in flames on a U.S. Forest Service dirt road between the Bear Mountain and Snow Summit ski resorts. A set of footprints in the snow led away from the burned truck. It took more than five hours for experts to confirm that it was Dorner's vehicle and search parties to begin a methodical sweep of an area stretching across eight square miles. While ski-masked SWAT teams went door-to-door checking hundreds of homes and shuttered cabins, other authorities fanned out on foot, slogging through fresh snow with search dogs. The teams combed backcountry and checked every shed, trash bin and barrel where the fugitive could hide. Dorner is described as African American, 6 feet tall and 270 pounds. The snow slowed the search, but did not halt it, said Cindy Bachman, a spokeswoman for the San Bernardino County Sheriff's Department. Sheriff John McMahon said the snow has one advantage: It is "great for tracking folks." Although following tracks led only to frustration Friday, authorities were relieved by the break in a week of extraordinary interconnected violence. Police say that Dorner has killed three people and injured others in a campaign to take revenge on those he blamed for his dismissal from the LAPD four years ago. Investigators are scrutinizing a conspiracy-laden manifesto that they believe was published on Dorner's Facebook page. In the screed, Dorner threatened "unconventional and asymmetrical warfare" against police officers and their families, saying that he has no choice but to kill to reclaim his damaged reputation. Police accuse him of killing the daughter of a retired LAPD captain and her fiance, who were found shot to death Sunday in a car in Irvine. While on the run, police said, Dorner shot three police officers, one fatally, in Riverside County. With warnings on radio and TV that an armed and deadly fugitive remained at large, police spent hours chasing down bogus leads and erroneous sightings. Dorner was purportedly driving a white Lexus near Barstow. He was supposedly spotted entering the county jail in downtown Los Angeles. He was allegedly holed up in a hotel in San Diego or in a park in Norco or at a home next to the Barona Indian Reservation in San Diego County. None of those tips checked out, and authorities are considering false reporting charges against one person who was more prankster than tipster. "When you're dealing with a case that's getting this amount of press coverage, you're going to get your share of bad information," said Laura Eimiller, a spokeswoman for the FBI, whose agents searched Dorner's home in Las Vegas and are investigating a package that CNN received, apparently from Dorner, that made various threats. Federal and local authorities also searched the home of his mother, Nancy Dorner, in La Palma, carrying out bags of potential evidence. With the possibility of Dorner in the vicinity and the potential for violence, the Bear Valley Unified School District closed all its campuses Friday, and nervous residents locked their doors and made other preparations. Roger Curtis, a retired carpenter who lives in Big Bear, said he was watching the manhunt on TV when a car alarm sounded. "I got the guns and loaded them," he said. Many residents suspect that Dorner high-tailed it out of the area, but others believe he could be hunkered down in one of many vacant, half-hidden cabins. Authorities can only speculate about Dorner's familiarity with the terrain and preparedness to brave a winter storm. Nancy Dorner owns property about 35 miles away in Arrowbear Lake, according to county records. Dorner, who was trained as a police officer and a Navy Reserve officer, learned to hunt in the Utah wilderness as a college student. As much as 8 inches of snow fell at higher elevations Friday. The National Weather Service predicts that temperatures will plunge to 16 degrees early Saturday, with the wind chill making it equivalent to -6. If Dorner were still hiding in the woods, he would need layered, insulated clothing - and have to avoid getting wet - to survive for very long, said Dr. Brian Prestwich, an assistant professor of clinical family medicine at USC's Keck School of Medicine. Cold weather poses a tremendous, and often unappreciated, threat to human survival. "The minute you're exposed to the cold air or you get wet, the clock starts ticking," Prestwich said. Dorner's five-hour-plus head start before the search got underway has brought extensive speculation about his whereabouts, including theories from his former boss, retired LAPD Police Chief William J. Bratton. Bratton and John Miller, a former LAPD official who is now a CBS correspondent, said they thought the burned truck was "possibly a diversionary tactic to draw people into that area while he's actually heading south." The former chief has good reason to be concerned about Dorner's location: In the package Dorner purportedly sent to CNN was a ceremonial coin with Bratton's name on it and three bullet holes - a discovery Bratton called "chilling." Police continue to guard at least 40 people mentioned in the anger-filled manifesto. Miller speculated that the burning of Dorner's pickup showed potential for calculated "pre-staging" and "planning." If this is premeditated staging, he said, "It makes you wonder: What is his plan for the end game?" Times staff writers Andrew Blankstein, Ari Bloomekatz, Eryn Brown, John Glionna, Anna Gorman, Robert Lopez, Kate Mather, Rick Rojas and Richard Winton contributed to this report.