It was first reported just before 1 am Wednesday at Highway 99 near Fresno Street.
California Highway Patrol officers say a man, later identifed as 24-year-old Oswald Capistron, was riding a scooter in the slow lane or near the right shoulder.
Moments later, Capistron was hit by at least three vehicles.
Capistron was pronounced dead at the scene.
It is not known if alcohol or drugs were involved in the crash.