Dorner was an LAPD officer from 2005 to 2008, when he was terminated, according to authorities.

The former officer claimed in a manifesto attributed to him that he was unfairly fired after reporting excessive force by a fellow officer, and he vowed to avenge his termination. He also served as a former U.S. Navy Reserve lieutenant who worked with river warfare units and a mobile inshore undersea warfare unit, according to Pentagon records obtained by CNN. His last day with the Navy was February 1.

Dorner is a suspect in a double murder Sunday in Irvine, California, authorities said. One victim was the daughter of retired Los Angeles Police Officer Randal Quan, who handled the appeal of Dorner's termination and, according to the manifesto, bungled it. Dorner appealed the case to a Los Angeles court, where a judge ruled against him in 2011, according to court records.

Multiple law enforcement agencies have linked Dorner, 33, to the shooting of two Riverside police officers in an ambush at an intersection around 1:30 a.m. Thursday. One officer, 34, died.

About 20 minutes earlier, police believe Dorner shot at two LAPD officers assigned to protect off-duty officers named in Dorner's manifesto, police said. A bullet grazed one of the officers, and the wound was not life-threatening. Damage to the squad car prevented the officers from pursuing Dorner, police said.

That shooting took place in Corona, also located in Riverside County, at 1:25 a.m. Thursday, said Los Angeles police.

For a former officer to be a suspected cop killer is beyond imagination for many law enforcement officers, whose culture bonds them so tightly that many can spot another officer out of uniform just by their demeanor and a nod of the head. The two sheriff's deputies acknowledged this subculture.

When asked how alarming it must be for a former officer to be at war with police, the younger deputy expressed acceptance.

"I guess it shows we're people too," he said.