A former Los Angeles cop with military training vowed war against other men in blue Thursday, leaving one officer dead days after he allegedly killed two other people to begin a wave of retribution for being fired, police said.

The focus of the intensive, expansive manhunt is Christopher Jordan Dorner, a 270-pound former Navy lieutenant who has professed his venom against LAPD officers he claimed ruined his life by forcing him out of his dream job.

Dorner blames one retired officer for bungling his appeal to get his job back in an 11-page manifesto, in which he also complained of mistreatment by the LAPD. In that letter -- provided to CNN by an LAPD source -- he vowed to violently target police officers and their families, whoever and wherever they are.

"I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," Dorner wrote.

"I never had the opportunity to have a family of my own, I'm terminating yours."

Authorities believe he followed through on his threats early Thursday by shooting a Riverside, California, police officer and two others. A day earlier, Irvine police named Dorner a suspect in the double slayings Sunday of a woman -- identified by Los Angeles police as the daughter of a retired LAPD officer -- and her fiance.

"My opinion of the suspect is unprintable," said Riverside police Chief Sergio Diaz, hours after one of his officers was killed. "The manifesto, I think, speaks for itself (as) evidence of a depraved and abandoned mind and heart."

The violence, as well as Dorner's background as a police officer and military trained marksman, left police on edge around Southern California.

In Torrance, LAPD officers guarding one of Dorner's alleged targets mistakenly opened fire on a blue pickup truck that resembled one Dorner was thought to be driving, said Los Angeles police Chief Charlie Beck.

The gunfire left two people wounded, Beck said. Torrance police also fired on another blue pickup, but no one was injured in that incident, according to a senior law enforcement source.

In downtown Los Angeles, police wearing body armor patrolled outside their own iconic headquarters.

Police have good reason to be fearful, the chief said.

"Of course, he knows what he's doing. We trained him," Beck said. "He was also a member of the armed forces. It is extremely worrisome and scary, especially to the officers involved."

The manhunt for Dorner spanned hundreds of miles and numerous counties. By Thursday afternoon, it was largely centered around Big Bear Lake -- about 100 miles east of Los Angeles -- where authorities found the truck the suspect allegedly used in the Riverside shooting.

Police confirmed that the vehicle, which was burnt out when it was found, belonged to Dorner by its vehicle identification number, San Bernardino County Sheriff John McMahon said.

This discovery spurred more officers to converge on the area to conduct beefed up patrols, staff checkpoints and go to every residence in the mountain community. McMahon acknowledged the fire may have been set as a diversionary tactic, though law enforcement isn't taking any chances. Early Thursday evening, he said that aerial and K9 searches on the ground will "continue as long as we can" -- though snow is coming -- and urged locals to be on alert.

"He could be anywhere at this point, and that's why we're searching door to door," the sheriff said.

1 cop dies in 'cowardly ambush'

It all started Sunday when Dorner allegedly killed two people in Irvine, according to police.

Police identified the victims as Monica Quan and her fiance Keith Lawrence.

Quan, 27, was the daughter of retired Los Angeles police Officer Randal Quan, LAPD Officer Tenesha Dobine told CNN. In his manifesto, Dorner said Quan handled his appeal.

On Tuesday, Dorner checked into the Navy Gateway Inns and Suites on San Diego's large naval base, Cmdr. Brad Fagan said.

Dorner likely had access to the hotel because he'd been honorably discharged from the Navy Reserve, said the Navy spokesman. Having retired February 1 as a lieutenant, Dorner worked with mobile inshore undersea warfare units and provided security on oil platforms in Iraq, according to Pentagon records. He was rated as a rifle marksman and pistol expert.

"He did not physically check out" Wednesday as expected, Fagan told reporters.

Police in San Diego say a man who could have been Dorner tried to hijack a boat there on Wednesday. Someone later found a wallet containing Dorner's identification and an LAPD detective's badge near the San Diego airport, according to police. It was unclear whether the badge was legitimate.