The male and female victims were in a parked car when shots rang out. Both victims were rushed to local hospitals, but the woman died from her injuries later. Her name has not been released.
The male victim's condition is unknown.
Witnesses said the car they were in appeared to be in some kind of chase with two other vehicles.
"It looked like the two trucks were chasing the white car because the white car was just like swerving side to side, trying to lose them," said witness Joel Topete.
Topete nearly found himself in the middle of the conflict when one of the cars clipped his driver's side mirror.
"My instincts were like, go chase them and see what's going on," he said.
However, Topete said he decided it wasn't worth it.
When police arrived at the scene, a Chevy Tahoe was in the middle of the street. Another witness told police they saw a gunman fleeing on foot.
Police do not believe the shooting was gang related.
Residents said in the past, there was some gang activity in the neighborhood, but recently, it's been pretty quiet, and the shooting caught them off guard.
Police do not believe the victims and the suspects were from the Walnut Park area.
Anyone with information is urged to call the L.A. County Sheriff's homicide detectives at (323) 890-5500.