The 53-year-old victim was found dead shortly after 3 a.m. Monday in the driver's seat of his taxi parked at an apartment complex off Interstate 80 northeast of Sacramento. Sheriff's spokesman Sgt. Tim Curran says he had at least one gunshot wound in his upper body.
Nearby residents told investigators that they heard two shots, but Curran says no one witnessed the shooting.
The name of the victim has not been released.
The Yellow Cab company is putting up a $15,000 reward for finding the killer, and authorities are adding another $1,000.