A manhunt has been launched as a fired policeman is suspected of gunning down five people and killing three and posting a manifesto on Facebook.
The ex-policeman declared all-out war on police officers and their families in a rambling Internet manifesto.
The violence began with the weekend slayings of a campus safety officer and his fiance.
The woman was the daughter of a retired Los Angeles police captain who represented the accused gunman in disciplinary proceedings.
The suspect blames the retired captain for his dismissal from the force.
The investigation widened in scope and urgency earlier this week when police learned that the suspect in that shooting, Christopher Dorner, 33, had posted an online declaration of grievances and threats which they have interpreted as a potential hit list.
The search for the suspect stretched from San Diego, where Dorner was believed to have tried to steal a boat last night, to the San Bernardino mountains northeast of Los Angeles.
Police descended on a ski area around the resort community of Big Bear Lake.
A truck matching a description of the suspect's getaway vehicle was found burning in the snow.
Nearby schools and other facilities were placed on a security lockdown as a precaution.
Police had closed in on Dorner earlier today when two Los Angeles police officers assigned to a security detail exchanged gunfire with him in the city of Corona.
One officer was grazed in the head by a bullet.
Two other officers were ambushed, with one killed, about 20 minutes later while sitting in their patrol car at a traffic light in the adjacent town of Riverside, about 60 miles (100 km) east of Los Angeles.
The officer who died was an 11-year veteran of the Riverside police force.
His partner was severely wounded but is expected to fully recover, the police said.
Mr Dorner, was fired from the Los Angeles Police Department in 2008 after more than three years as an officer, was presumed to be armed with multiple weapons, including an assault rifle.
LAPD said the threats contained in Dorner's rambling, multi-page manifesto posted to Facebook had prompted police to dispatch more than 40 security details to protect people thought to be in danger of attack.