Boyer and Hazel were responding to a traffic collision around 8:30 a.m. Monday when the shooting happened, according to sheriff's Lt. John Corina.
Boyer is a 27-year veteran of the department.
Boyer was the third Whittier police officer killed in the line of duty, according to the department.
"It seems like a simple traffic accident and next thing they know they're in a gunfight", Corina said, adding that "you never know when you respond to a call, what you are going to run into".
The Whittier Police Department has about 125 sworn officers who patrol Whittier and Santa Fe Springs.
Corina said witnesses identified the shooter as possibly the gunman involved in a murder earlier Monday involving a stolen auto the gunman ultimately crashed in Whittier.
Sheriff's deputies are investigating the incident.
The victim in that shooting was identified as Roy Torres, 49, who was reported to be a cousin of the gunman.
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The officers were able to wound the suspect who's name was not released.
That driver had gotten out and asked those he had hit to help push his stolen auto from the intersection, investigators said.
The surviving officer and suspect are now in stable condition, according to Corina.
When officers approached the suspect, he was sitting in his vehicle. The officers returned fire and wounded him.
The suspect, who was driving a vehicle allegedly stolen out of East L.A., had rear-ended a auto on Colima Road and Mar Vista Street, a sheriff's news release stated. The suspect's gun was recovered at the scene, Corina said. "This is a senseless, senseless tragedy that did not need to be". One driver - in a stolen vehicle - opened fire on officers.
The chief also said Boyer's killing showed how California's laws make the streets less safe. "And I didn't think I had any tears left". And especially for the family and friends of Officer Keith Boyer, who was shot to death Monday.
Corina didn't immediately know why the gang member had been released early. She said he had a criminal history that dated back to when he was a child.
"He was the best of the best", Piper said tearfully during a Monday afternoon news conference. Enough is enough. You're passing these propositions, you're creating these laws.