Police vowed Thursday to keep searching for an ex-cop accused of killing three people, including another officer, as night fell over a California ski resort where his burnt-out truck was found.
Some 125 officers were deployed in and around Big Bear, east of Los Angeles, where police found the Nissan pickup truck belonging to Christopher Dorner, 33, who had posted a chilling online manifesto.
"We'll keep working on it until we're able to either locate the suspect, or determine that he's no longer in the Big Bear Valley," said San Bernardino County Sheriff John McMahon, as schools and ski lifts were put on lockdown.
"We did find some tracks around the vehicle, but they did not lead to the suspect... we are committed to continuing this operation."
It also emerged that Dorner had sent a package a week ago to CNN host Anderson Cooper, with a note saying "I never lied," a DVD and a coin shot through with bullet holes, the news anchor said.
Dorner was wanted over Sunday's suspected revenge killing of a couple, Keith Lawrence and Monica Quan. The woman was the daughter of Randy Quan, a retired police officer Dorner blamed for his firing five years ago.
The suspect then allegedly attacked two other officers overnight Wednesday in Riverside, killing one and injuring the other. Another officer was injured in a separate incident in nearby Corona.
In addition, two civilians were injured early Thursday when police officers opened fire on them in a vehicle they believed to be Dorner's.
In an Internet manifesto threatening police and their families, Dorner had warned about "terminating" Quan and called lesbians and Asians "high-value" targets.
"I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," he said.
The LA Police Department, backed by agencies including the FBI, said it was protecting over 40 possible targets, some of them identified in the "rambling" online manifesto by Dorner, a US Navy reservist.
"Dorner is considered to be armed and extremely dangerous," LAPD chief Charlie Beck told a press conference, adding that the suspect has "multiple weapons at his disposal, including assault rifles."
Dorner's wallet and an ID badge were found overnight in San Diego, two hours south of Los Angeles, police said, while there were also reports of police searches in neighboring Nevada, where he has a house near Las Vegas.
Shortly after midday, authorities in Big Bear put schools and a ski area on lockdown, after the pickup truck matching the description of Dorner's was found in nearby woods.
Television networks broadcast footage showing armed police apparently fanning out across a mountain slope, although the LAPD quickly asked broadcasters not to show live footage, to avoid giving Dorner help if he was monitoring the media.
Dorner posted his manifesto online Monday, saying he was not afraid to die because he had already in effect died when he was dismissed in September 2008 for making false statements about his training officer.
"I never had the opportunity to have a family of my own, (so) I am terminating yours," he wrote to Quan.
"Suppressing the truth will (lead) to deadly consequences for you and your family. There will be an element of surprise where you work, live, eat and sleep," he added, referring to Quan and several others.
Dorner is described as black, six feet (1.80 meters) tall and 270 pounds (120 kilograms) in weight.
LAPD assistant chief Mike Moore traveled up to Big Bear to join the manhunt, which involved officers from several other forces. "This complex and violent investigation has led to this mountain," he said.
"We are committed to sharing every bit of information, working in concert with them, in apprehending this individual... to help these men and women up here tonight to find this individual."
Beck, the LAPD chief, said Dorner's police and military training made the threat all the more serious.
"He knows what he's doing. We trained him... he's also a member of the armed forces," Beck said. "It is extremely worrisome and scary."