** UPDATE: Police held a press conference, updating the situation. They say Dorner is considered armed and dangerous.

In an online manifesto, Dorner wrote that he plans to "bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

A massive manhunt is ongoing for a former LAPD officer and U.S. Navy reservist suspected of killing a woman and her fiance, and then opening fire on three police officers, killing one. Police believe 33-year-old Christopher Jordan Dorner is armed and dangerous.

Watch the latest update from reporter Dominic Di-Natale on America's Newsroom.

Stay tuned to Fox News Channel for all of the latest updates on the manhunt.

Here's some more background on the developing story from FoxNews.com:

A multi-agency manhunt is under way in California after police say the former Los Angeles police officer suspected in the murders of a college basketball coach and her fiancé last weekend opened fire Wednesday night on three police officers, killing one, KTTV.com reported.

The suspect has been identified as Christopher Jordan Dorner, 33, and he is considered extremely dangerous, authorities say. The killings appear to be retribution for his 2009 termination from the Los Angeles Police Department, authorities say.

Details of the shooting involving the police officers remain unclear, but KTTV.com reported that one officer was killed and another is undergoing surgery. The Riverside County Sheriff’s Department confirmed to Fox News that two Riverside officers were shot and possibly an LAPD officer in Corona.

Read more at FoxNews.com .