The Los Angeles County Sheriff's Department says a disturbance between a boyfriend and girlfriend sent Monterey Park police to a motel shortly after midnight Friday.
Officers arriving at the motel saw a car leave and two patrol cars pulled it over.
Investigators say at that point, a passenger got out and brandished a handgun.
He was shot and died at the scene. His name hasn't been released.
Authorities say they found a gun at the scene.
No officers were hurt.