BIG BEAR LAKE, California (AP) - The search resumed in the snowy California mountains Saturday for a former police officer who is suspected of killing three in a deadly rampage to get back at those he blames for ending his career.
The manhunt for Christopher Dorner entered its fourth day. Relentless snowfall on Friday grounded helicopters with heat-sensing technology. Dorner's burned-out truck was found a day earlier in a ski resort town. Attempts to follow his tracks failed.
Police teams in camouflage were scouring the mountains, aware they could be walking into a trap set by the well-trained former U.S. Navy reservist.
"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."
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 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 Los Angeles Police Department and its families.
According to documents from a court of appeals hearing, Dorner was fired after he made a complaint against his field training officer, saying that said that in the course of an arrest, she kicked suspect Christopher Gettler, a schizophrenic with severe dementia.
Richard Gettler, the schizophrenic man's father, gave testimony that supported Dorner's claim. After his son was returned home on July 28, 2007, Richard Gettler asked "if he had been in a fight because his face was puffy" and his son responded that he was kicked twice in the chest by a police officer.
Dorner was fired in 2008 over the incident. On Sunday, police say Dorner shot and killed a couple in a parking garage. The woman was the daughter of a retired police captain who had represented Dorner in the disciplinary proceedings that led to his firing.
Hours after authorities identified Dorner as a suspect in the double murder, police believe Dorner shot and grazed an LAPD officer and then used a rifle to ambush two police officers early Thursday, killing one and seriously wounding the other.
The focus of the manhunt was on the mountains 80 miles (128 kilometers) east of Los Angeles -- a snowy wilderness, filled with thick forests and jagged peaks.
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."
Jamie Usera, an attorney who befriended Dorner in college, said he introduced him to the outdoors and taught him 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. It was 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.
Police believe he is 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 Christopher Weber, Greg Risling, Michael Blood, John Antczak and Julie Watson.