The brothers, ages 8 to 12, were found dead of multiple stab wounds in the back of an SUV in a gruesome scene, Los Angeles Police Chief Charlie Beck said.
The boys' father was bleeding from stab wounds to his chest in the front seat and was taken to a hospital in critical condition. The children were later taken to a coroner's office.
Homicide detectives believe the father, whose name was not released, killed the boys, Officer Matthew Ludwig said, adding that he will be arrested if he survives his wounds.