The fallen officer was identified as Keith W. Boyer, a 27-year veteran of the Whittier Police Department. Whittier is about 17 miles southeast of Los Angeles.
A second Whittier officer who responded to the accident was wounded, according to Lt. John Corina of the Los Angeles County Sheriff's Department.
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identified that officer as Patrick Hazell, a member of the force for three years. He was in stable condition at a hospital, police said.
The unidentified suspect was injured in an exchange of gunfire. He was in intensive care, police said.
Authorities said the suspect and another driver were involved in the accident about 8:30 a.m. Monday. Corina said the two Whittier officers responded to the scene. They ordered the suspect out of the car.
Corina said officers went to check the suspect for a weapon because they could see he had tattoos over his face and neck and had "gang attire."
"As they went to pat him down for any weapons, that's when he pulled out his gun and that's when he started shooting," Corina said.
The suspect was driving a stolen car from East Los Angeles, Corina said. The suspect was identified as being involved in an earlier fatal shooting there, the lieutenant said.
Corina said the officers, who were wearing protective vests, didn't know the car was stolen or that the driver may have been involved in criminal activity.
Authorities said the suspect was released on parole about a week ago. Officials did not reveal details on his conviction or his parole.
"I won't speak about the suspect, because frankly I don't think he's worth speaking about," Whittier police Chief Jeff Piper said.
Officer was 'best of the best'
"I can honestly say on behalf of all the officers, he was the best of the best," Piper said of Boyer. "Our community knows him, and they would say the same thing."
Boyer, who died at a hospital, was a "a fantastic officer" who climbed the ranks from a job as a dispatcher. "Keith was very humble," Piper said.
A divorced father of grown children, Boyer had recently talked about retirement, Piper said.
The chief said he had played in a band with Boyer, who was a drummer.
At one point, Piper broke down.
"It's really hard for me to hold back my tears because all of us have been grieving since 10 this morning, and I didn't think I had any tears left," he said.
Piper said Boyer was the first officer the department has lost since the late 1970s. He was at least the fifth US law enforcement officer to be fatally shot in the line of duty this year, according to the National Law Enforcement Officers Memorial Fund
Condolences for Boyer and best wishes for Hazell's recovery poured in from law enforcement.