The crash happened just after 2 p.m. Saturday on State Route 23 near Los Angeles Avenue.
According to the California Highway Patrol, the driver of a Chevrolet was speeding along the center median before losing control, crossing into oncoming traffic and crashing into a Lexus sedan.
CHP said the passenger in the Chevrolet was ejected and died at the scene. The driver of the Lexus also died there.
Jay Shields, a man who witnessed the crash while teaching his son how to drive, saw the events unfold.
"I was teaching him how to drive, literally, right before this accident," Shields said. "So you ask if there's a message here ... physically injuring someone, or even paying a ticket, is not worth the 20 seconds you may gain from speeding."
Meantime, two other people were sent to the hospital with serious injuries. The driver of the Chevrolet suffered moderate injuries.
No arrests have been made.
The collision remains under investigation.