According to police, a Honda was headed north on Alameda when it was struck by a Dodge pickup truck headed west on Vernon. The driver of the pickup truck fled the scene.
The suspect, who was reportedly alone in the truck, was later arrested and booked on suspicion of hit and run. Police withheld his name.
Three people in the Honda were killed in the crash. Their names were not released.
A 6-year-old boy who was also in the Honda was taken to a hospital and was expected to be OK.
Anyone who saw what happened was asked to call police at (323) 587-5171.
City News Service contributed to this report.