A second officer who was also shot is in stable condition Saturday.
The Los Angeles County Sheriff's Department said the officers were responding to a call in Pomona around 9 p.m. Friday. Pomona is about 30 miles (48 kilometers) east of Los Angeles in Los Angeles County.
Police Chief Michael Olivieri tweeted overnight that one of the officer had not survived.
Authorities have not released any more information including whether the suspect is in custody.
Police remained on the scene Saturday morning.