The bustling winter resort of Big Bear took on the appearance of a ghost town Thursday as surveillance aircraft buzzed overhead and police in tactical gear and carrying rifles patrolled mountain roads in convoys of SUVs, while others stood guard along major intersections. 
 
 Even before authorities had confirmed that the torched pickup truck discovered on a quiet forest road belonged to suspected gunman Christopher Dorner, 33, officials had ordered an emergency lockdown of local businesses, homes and the town's popular ski resorts. Parents were told to pick up their children from school, as rolling yellow buses might pose a target to an unpredictable fugitive on the run. 
 
 By nightfall, many residents had barricaded their doors as they prepared for a long, anxious evening. 
 
 PHOTOS: A tense manhunt amid tragic deaths 
 
 "We're all just stressed," said Andrea Burtons as she stocked up on provisions at a convenience store. "I have to go pick up my brother and get him home where we're safe." 
 
 Police ordered the lockdown about 9:30 a.m. as authorities throughout Southern California launched an immense manhunt for the former lawman, who is accused of killing three people as part of a long-standing grudge against the LAPD. Dorner is believed to have penned a long, angry manifesto on Facebook saying that he was unfairly fired from the force and was now seeking vengeance. 
 
 Big Bear manhunt: In the Feb. 8 LATExtra section, an article about the manhunt for ex-LAPD officer Christopher Dorner said that Big Bear has roughly 400 homes, and that authorities guessed that only 40% are occupied year-round. In fact, authorities planned to search 400 homes, of which 40% are vacation homes not occupied year-round. Big Bear Lake, where the search is taking place, has about 9,000 homes, according to the 2010 Census 
 
 Forest lands surrounding Big Bear Lake are cross-hatched with fire roads and trails leading in all directions, and the snow-capped mountains can provide both cover and extreme challenges to a fugitive on foot. It was unclear whether Dorner was prepared for such rugged terrain. 
 
 Footprints were found leading from Dorner's burned pickup truck into the snow off Forest Road 2N10 and Club View Drive in Big Bear Lake. 
 
 San Bernardino County Sheriff John McMahon said that although authorities had deployed 125 officers for tracking and door-to-door searches, officers had to be mindful that the suspect may have set a trap. 
 
 "Certainly. There's always that concern and we're extremely careful and we're worried about this individual," McMahon said. "We're taking every precaution we can." 
 
 PHOTOS: A fugitive's life on Facebook 
 
 Big Bear has roughly 400 homes, but authorities guessed that only 40% are occupied year-round. 
 
 The search will probably play out with the backdrop of a winter storm that is expected to hit the area after midnight. 
 
 Up to 6 inches of snow could blanket local mountains, the National Weather Service said. 
 
 FULL COVERAGE: Sweeping manhunt for rampaging ex-cop 
 
 Gusts up to 50 mph could hit the region, said National Weather Service meteorologist Mark Moede, creating a wind-chill factor of 15 to 20 degrees. 
 
 Extra patrols were brought in to check vehicles coming and going from Big Bear, McMahon said, but no vehicles had been reported stolen. ||||| A Northridge, Calif., home improvement store was evacuated tonight because of a possible sighting of suspected cop-killer Christopher Dorner, just hours after police announced a $1 million reward for information leading to his arrest. 
 
 As helicopters hovered overhead and a command center was established, police searched the Lowe's store and eventually told shoppers they could leave, but could not take their cars out of the parking lot. 
 
 LAPD spokesman Gus Villanueva said the major response to the possible sighting was a precaution, but couldn't say whether Dorner was in the area. 
 
 The announcement of the $1 million reward today came as authorities in Big Bear, Calif., scaled back their search for Dorner, the disgruntled ex-cop who is suspected in three revenge killings. 
 
 "This is the largest local reward ever offered, to our knowledge," Los Angeles Police Chief Charlie Beck said at a news conference today. "This is an act of domestic terrorism. This is a man who has targeted those that we entrust to protect the public. His actions cannot go unanswered." 
 
 The money for the reward was pooled by businesses, government, local law enforcement leaders and individual donors, Beck said. 
 
 PHOTOS: Former LAPD Officer Suspected in Shootings 
 
 The reward comes on the fourth day of a manhunt for Dorner, who has left Southern California on edge after he allegedly went on a killing spree last week to avenge his firing from the police force. Dorner outlined his grievances in a 6,000 word so-called "manifesto" and said he will keep killing until the truth is known about his case. 
 
 Dorner's threats have prompted the LAPD to provide more than 50 law enforcement families with security and surveillance detail, Beck said. 
 
 Authorities are chasing leads, however they declined to say where in order to not impede the investigation. 
 
 Dorner's burned-out truck was found Thursday near Big Bear Lake, a popular skiing destination located 80 miles northeast of Los Angeles. 
 
 Investigators found two AR-15 assault rifles in the burned-out truck Dorner abandoned, sources told ABC News. 
 
 The truck had a broken axle, which may be the reason he decided to set fire to it, the police sources said. 
 
 Full Coverage: Christopher Jordan Dorner 
 
 Officers have spent the past couple of days going door-to-door and searching vacant cabins. The manhunt was scaled back to 25 officers and one helicopter in the resort town today, according to the San Bernadino Sheriff's Office. 
 
 On Saturday, Beck announced he would reopen the investigation into Dorner's firing but said the decision was not made to "appease" the fugitive ex-cop. 
 
 "I feel we need to also publicly address Dorner's allegations regarding his termination of employment, and to do so I have directed our Professionals Standards Bureau and my Special Assistant for Constitutional Policing to completely review the Dorner complaint of 2007; To include a re-examination of all evidence and a re-interview of witnesses," Beck said. "We will also investigate any allegations made in his manifesto which were not included in his original complaint." 
 
 Dorner is suspected of killing Monica Quan and her fiancé Keith Lawrence last Sunday in their car in the parking lot of their Irvine, Calif., condominium complex. Both were struck with multiple gunshot wounds. 
 
 Quan's father, Randal Quan, was a retired captain with the LAPD and attorney who represented Dorner before a police review board that led to Dorner's dismissal from the force in 2008. 
 
 On Wednesday, after Dorner was identified as a suspect in the double murder, police believe he ambushed two Riverside police officers, killing one and wounding the other. 
 
 The next day, Randal Quan reported he received a taunting call from a man claiming to be Dorner who told him that he "should have done a better job of protecting his daughter," according to court documents documents. 
 
 Anyone with information leading to the arrest of Christopher Dorner is asked to call the LAPD task force at 213-486-6860. 
 
 ABC News' Dean Schabner, Jack Date, Pierre Thomas, Jason Ryan and Clayton Sandell and The Associated Press contributed to this report. ||||| The hunt for Christopher Dorner in the snow-covered San Bernardino Mountains is expected to resume at daybreak Saturday, when authorities hope clearer skies will allow airplanes to help them in their search. 
 
 Members on the California Highway Patrol search a truck for Christopher Dorner, a former Los Angeles police officer accused of carrying out a killing spree because he felt he was unfairly fired from his... (Associated Press) 
 
 This undated photo released by the Los Angeles Police Department shows suspect Christopher Dorner, a former Los Angeles officer. Dorner, who was fired from the LAPD in 2008 for making false statements,... (Associated Press) 
 
 Police investigators take away evidence from the home of the mother of fugitive suspect former Los Angeles police officer Christopher Dorner, in La Palma, Calif., on Friday, Feb. 8, 2013. Police agencies... (Associated Press) 
 
 A digital billboard along Santa Monica Boulevard on the west side of Los Angeles shows a "wanted" alert for former Los Angeles police officer Christopher Dorner Friday, Feb. 8, 2013. Dorner is suspected... (Associated Press) 
 
 A San Bernardino County Sheriff SWAT team returns to the command post at Bear Mountain near Big Bear Lake, Calif. after searching for Christopher Jordan Dorner on Friday, Feb. 8, 2013. Search conditions... (Associated Press) 
 
 A San Bernardino County Sheriff SWAT team returns to the command post at Bear Mountain near Big Bear Lake, Calif. after searching for Christopher Jordan Dorner on Friday, Feb. 8, 2013. Search conditions... (Associated Press) 
 
 A San Bernardino County Sheriff SWAT team returns to the command post at Bear Mountain near Big Bear Lake, Calif. after searching for Christopher Jordan Dorner on Friday, Feb. 8, 2013. Search conditions... (Associated Press) 
 
 ADDS DATE VIDEO WAS TAKEN - This image provided by the Irvine Police Department shows Christopher Dorner from Jan. 28, 2013 surveillance video at an Orange County, Calif., hotel. More than 100 officers,... (Associated Press) 
 
 Relentless snowfall on Friday grounded helicopters with heat-sensing technology and hampered their effort to find the former Los Angeles police officer suspected of going on a deadly rampage to get back at those he blamed for ending his career. 
 
 After they found his burned-out pickup truck near at this ski resort town Thursday afternoon, SWAT teams in camouflage started scouring the mountains, aware to the reality 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. 
 
 "He can be behind every tree," said T. Gregory Hall, a retired tactical supervisor for a special emergency response team for the Pennsylvania State Police. "He can try to draw them into an ambush area where he backtracks." 
 
 As authorities weathered heavy snow and freezing temperatures in the mountains, thousands of heavily armed police remained on the lookout throughout California, Nevada, Arizona and northern Mexico for a suspect bent on revenge and willing to die. 
 
 Police said officers still were guarding more than 40 people mentioned as targets in a rant they said Dorner posted on Facebook. He vowed to use "every bit of small arms training, demolition, ordnance and survival training I've been given" to bring "warfare" to the LAPD and its families. 
 
 The manhunt had Southern California residents on edge. Unconfirmed sightings were reported near Barstow, about 60 miles north of the mountain search, and in downtown Los Angeles. 
 
 Some law enforcement officials said he appeared to be everywhere and nowhere, and speculated 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 thick forests and jagged peaks, that creates peril as much for Dorner as the officers hunting him. 
 
 The small army hunting him has the advantage of strength in numbers and access to resources, such as special weapons, to bring him in. 
 
 In his online rant, Dorner baited authorities. 
 
 "Any threat assessments you generate will be useless," it read. "I have the strength and benefits of being unpredictable, unconventional, and unforgiving." 
 
 Without the numbers that authorities have, Dorner holds one advantage: the element of surprise. 
 
 Authorities said they do not know how long Dorner had been planning the rampage or why he drove to the San Bernardino Mountains. Property records show his mother owns undeveloped land nearby, but a search of the area found no sign of him. 
 
 It was not clear if he had 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. ... Not everybody is survivor-man." 
 
 Jamie Usera, an attorney in Salem, Ore., who befriended Dorner when they were students and football teammates at Southern Utah University, said he introduced him to the outdoors. Originally from Alaska, Usera said, he taught Dorner about hunting and other outdoor activities. 
 
 "Of all the people I hung out with in college, he is the last guy I would have expected to be in this kind of situation," Usera, who had lost touch with Dorner is recent years, told the Los Angeles Times. 
 
 Others saw Dorner differently. Court documents obtained by The Associated Press on Friday show an ex-girlfriend of Dorner's called him "severely emotionally and mentally disturbed" after the two split in 2006. 
 
 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 six-month 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 riddled with bullet holes that former Chief William Bratton gave out as a souvenir was also in the package. 
 
 Police said it was a sign of planning by Dorner before the killing began. 
 
 On Sunday, police say Dorner shot and killed 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. 
 
 Hours after authorities identified Dorner as a suspect in the double murder, police believe Dorner shot and grazed an LAPD officer in Corona and then used a rifle to ambush two Riverside police officers early Thursday, 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, said LAPD Deputy Chief Kirk Albanese. 
 
 As a result, 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." 
 
 ___ 
 
 Associated Press writers contributing to this report include Michael Blood and John Antczak in Los Angeles and Julie Watson in San Diego. 
 
 Risling reported from Big Bear Lake and Abdollah reported from Los Angeles. She can be reached on Twitter at http://www.twitter.com/LATams
– The California resort town of Big Bear Lake has had a rough night. Los Angeles police officers have visited more than half the area's homes as they search for ex-cop Christopher Dorner; they're telling locals not to answer their doors unless they're sure who's knocking, ABC News reports. Meanwhile, surveillance aircraft are patrolling the skies and fleets of SUVs are keeping watch on the roads as the town is in lockdown, the Los Angeles Times reports. Police say they found Dorner's pickup truck torched on a forest road, with footprints trailing away through the snow. That snow could help hide Dorner, but could also make any movements on foot difficult, the Times notes. More details about Dorner's past are emerging: While longtime acquaintances recalled a "typical guy" who was "never disgruntled," police had long been concerned about him. Four years ago, when he faced a disciplinary hearing the day he was fired from the department, armed guards were on hand, the Times adds. "It was clear ... that he was wound way too tight," an officer says. Click to read about the bizarre package Dorner reportedly sent Anderson Cooper.