* Former Navy officer accused of three murders
* Suspect declared war on police in online manifesto
* Slayings seen as vengeance for 2008 LAPD dismissal (Adds details from afternoon news conference, paragraphs 8, 10, 12-13)
By Brandon Lowrey
BIG BEAR LAKE, Calif., Feb 8 (Reuters) - Heavy snow hampered the second day of a mountaintop manhunt on Friday for a fugitive former policeman wanted as a suspect in three California murders and accused of declaring war on police in an Internet manifesto that railed against his 2008 firing.
As investigators sought clues to whether Christopher Dorner was holed up in the rugged San Bernardino mountains east of Los Angeles or had slipped away undetected, police across the region continued to chase down unconfirmed sightings and dead-end leads.
Police have said they believe Dorner was carrying multiple weapons, including an assault-style rifle, though the Facebook manifesto attributed to him suggested he might be more heavily armed.
"Do not deploy airships or gunships. SA-7 Manpads will be waiting," the message said, in a reference to a Russian-made shoulder-launched missile system.
The manhunt focused on the snow-swept wooded hillsides and cabins near the community of Big Bear Lake, a popular ski resort about 80 miles northeast (129 km) of Los Angeles where Dorner's pickup truck was found abandoned and set on fire on Thursday.
The truck turned up in the mountains hours after police say Dorner exchanged gunfire with two officers, grazing one, and later ambushed two more policemen in their patrol car at a stoplight, killing one and leaving the other badly wounded.
A former Navy lieutenant, he is also suspected in the weekend shooting deaths of a campus security officer and his fiancée, the daughter of a retired Los Angeles police captain singled out for blame in Dorner's manifesto for his dismissal from the LAPD.
The heavy snowfall around Big Bear slowed the pace of the manhunt and prevented infrared-equipped helicopters from returning to the skies. But a team of more than 100 law enforcement officers, some of them riding in "snowcat" tractor vehicles and armored personnel carriers, kept up a ground search with dogs.
San Bernardino County Sheriff John McMahon said the manhunt would press on "until either we discover that he's left the mountain or we find him."
Search teams initially followed footprints identified as Dorner's that led from the truck into the forest "until we lost them where the ground got frozen and we couldn't continue to track," McMahon said.
Lacking air support, authorities planned to call off the mountain search after sundown and to resume it at daybreak on Saturday, said Cindy Bachman, the sheriff's spokeswoman. A door-to-door search of more than 200 vacant cabins dotting the high country above town was expected to be completed by nightfall.
"We just want to make sure he doesn't find a place to hide out," McMahon said.
'ALMOST LIKE A HORROR MOVIE'
Ski resorts and businesses in the area remained open, though visitors seemed to acknowledge they were tempting fate.
"It's almost like a horror movie," said Cayle Rose, 23, who was visiting the area from Beverly Hills. "We're a bunch of young people headed up to a cabin in the woods, and there's a snowstorm and a madman on the loose."
Bachman conceded that there was uncertainty about Dorner's whereabouts, saying: "There's a possibility that he's still here, and the possibility exists that he did leave."
Area schools that were shut down on Thursday as a precaution remained closed due to snow.
As speculation mounted that Dorner might have quietly left the mountains, perhaps using his torched truck as a decoy, reports of unconfirmed sightings sprang up across Southern California - from the desert town of Barstow to the seaside city of San Diego.
In Los Angeles, a sheriff's department employee reported seeing a man she thought resembled Dorner in a parking structure outside the city's main jail, prompting a lockdown of the facility while deputies searched the area, sheriff's spokesman Steve Whitmore said.
The jail commander, Paul Pietrantoni, confirmed to reporters that Dorner's ex-wife works at the facility.
Police said they were providing extra security protection for about 40 potential targets mentioned in the online declaration.
Dorner first came to public attention on Wednesday when he was named as a suspect in the slayings of a university security officer and his fiancée, college basketball coach Monica Quan, in Irvine, about 40 miles (64 km) south of Los Angeles. They were found shot to death on Sunday in a car at the top of a parking structure.
Quan, 28, was the daughter of a retired Los Angeles police captain who represented Dorner in disciplinary action that led to his 2008 firing for making false statements accusing another officer of using excessive force.
Two Los Angeles police officers assigned to a search detail traded gunfire with him early on Thursday in the city of Corona, east of Los Angeles, some 20 minutes before the two other officers were ambushed in the adjacent town of Riverside.
The FBI said its agents had searched a Las Vegas residence owned by Dorner, who joined the Navy in 2002 and the LAPD in 2005. He was discharged from the Navy Reserves last Friday, two days before Quan and her fiance were found slain.
Dorner, who once played college football, blamed the police department not just for firing him but also for ending his Navy career and the loss of close relationships. (Additional reporting by Dana Feldman and Steve Gorman; Writing by Steve Gorman; Editing by Daniel Trotta, Alden Bentley, Cynthia Johnston, Leslie Gevirtz, Chizu Nomiyama and Paul Simao)