"We had some preliminary reports from witnesses that this may have been a speed contest or drag racing," said Westminster Police Sgt. Cameron Knauerhaze.
Police say a red Toyota was racing another car, lost control, and never slowed down. There were almost no skid marks on the ground.
"It appears right now that this Honda behind me was an innocent bystander that was driving northbound up Hoover when this red car lost control, came into its lanes," Knauerhaze said.
A yellow tarp covered the body of the Toyota's passenger, 18-year-old Jessica Dayoan, who died on scene. Her brother, 19-year-old Jorel Dayoan, was the driver. Their father and sister arrived on scene, clearly shook up.
Meanwhile, both drivers were rushed to local trauma centers in serious condition after being cut out of the wreckage.
Police are also trying to find the driver of the other car who they believe the Dayoans were racing. The car apparently left the scene immediately after the crash.
Officers hope the unfortunate accident sends a message to those thinking about drag racing.
"Driving a car is a big responsibility as you can see, in a moments' notice, an innocent bystander's life was completely changed," Knauerhaze said.
Anyone with information about the crash should call the Westminster Police Department at (714) 898-3315.