The teen, identified by the Contra Costa County coroner's office as 19-year-old Justin Deyoung, apparently tried to jump onto the slow-moving sport utility vehicle at the last minute, Danville Police Chief Steve Simkins said.
Deyoung somehow slipped and fell and died at the scene, police said.
Simkins said it is not yet clear whether he was killed in the fall or if the car ran over him. An autopsy will be conducted today or Tuesday.
He said it does not appear that alcohol or drugs contributed to the accident.
Deyoung was apparently standing near the intersection of Del Amigo and Glen roads just before midnight when a Toyota Sequoia filled with an unknown number of his friends pulled up to him.
His friends told him where they were going so he could meet them there, and the Sequoia began to pull away slowly. Deyoung then apparently decided to try to jump onto the side of the SUV and ride along with it but fell, Simkins said.
The distraught driver was one of the people who called 911, police said. Deyoung was pronounced dead at the scene.
Simkins emphasized that this was not a case of "car surfing" or "ghost riding," dangerous stunts performed on moving cars. He said it appears the teen decided to jump onto the car spontaneously.
"It was a last-minute, bad decision," Simkins said. "I have three boys myself, so it's heartbreaking to see a parent lose their child."
Police are still interviewing witnesses to the accident. They left the scene at about 5 a.m. but will continue to canvass the neighborhood, Simkins said.