Williams was asleep near the Fifth Street off-ramp from westbound I-80 when the accident occurred around 1:10 a.m., according to California Highway Patrol.
Police identified Jaime Juarez, 27, as the driver of the Toyota SUV that struck Williams. Juarez allegedly drove off the road and onto the dirt embankment where Williams was sleeping.
Juarez was arrested on suspicion of felony DUI and vehicular manslaughter and booked into County Jail.
Williams was pronounced dead at the scene of the accident.