The cabin in the mountains above Los Angeles went up in flames after the gunman, suspected of a killing spree that has targeted police and their families, took refuge following a car chase with police, officials said on Wednesday.
Police were awaiting forensic analysis to confirm the body was that of Dorner, the subject of the six-day manhunt that has ranged across southern California.
San Bernardino County Sheriff's spokesperson Cindy Bachman told reporters on Tuesday night that the 33-year-old former Los Angeles police officer who barricaded himself inside the cabin and exchanged gunfire with officers was thought to be Dorner and that "we believe he was still inside" when it went up in flames.
A sheriff's deputy was killed in the shootout in the snow-covered, wooded hills of the San Bernardino National Forest, north-east of Los Angeles, bringing to four the number of killings Dorner is suspected of committing. A second sheriff's deputy was wounded in Tuesday's gunfight.
An angry manifesto posted last week on Dorner's Facebook page claimed he had been wrongly terminated from the Los Angeles police department in 2008. He vowed to seek revenge by unleashing "unconventional and asymmetrical warfare" on officers and their families.
Tuesday's climax to the saga unfolded after police learned that a gunman they believed was him had broken into a home near the ski resort community of Big Bear Lake, tied up a couple and stolen their vehicle.
State game wardens later spotted the vehicle and gave chase. The suspect crashed the car, then commandeered a bakkie at gunpoint from another motorist, said Lieutenant Patrick Foy of the state fish and wildlife department.
As game wardens pursued him, the suspect fired at them from the window of the truck, and one of the game officers stopped his truck and fired back with a high-powered rifle, Foy said, adding that he did not know whether the man was hit.
Exhaustive manhunt
Officers got close enough at one point during the chase to recognise the driver as Dorner, Foy said. He ultimately abandoned the car and fled on foot into the woods to a cabin believed to be vacant, where he holed up inside and exchanged fire with sheriff's deputies.
After a lull in the gunfire, the cabin suddenly caught fire, with smoke and flames seen engulfing the structure. Loud popping sounds could be heard from inside.
The department's Chief Charlie Beck has called the search for Dorner the most extensive manhunt in the region's history and a spokesperson said that some 50 families considered his potential targets would remain under guard for the time being.
"Until Dorner has been identified or we have him in handcuffs we're going to continue as if he's still out there," Commander Andrew Smith said.
Dorner's last confirmed encounter with authorities came early last Thursday, when police said he ambushed two policepeople at a traffic light in Riverside, about 100km east of Los Angeles. One officer was killed and the other wounded.
The former US Navy officer, is also suspected of exchanging gunfire on Thursday with police and wounding one officer in nearby Corona.
He first came to public notice last Wednesday when police identified him as a suspect in the slayings of a campus security officer and his fiancée, the daughter of a retired Los Angeles police captain. In the manifesto posted on his Facebook page, Dorner blamed the captain for his dismissal from the police department.
Authorities posted a $1-million reward for information leading to Dorner's capture, an amount they said was the largest ever offered in a Southern California criminal investigation. – Reuters