He had been crossing El Camino from east to west at Almendral Avenue, Sgt. Sherman Hall of the Atherton Police Department told the Almanac.
He was struck in the southbound slow lane by a Volvo S40 driven by a 17-year-old girl from San Carlos, police said. The driver's name was not released because she is a minor.
A witness told police that Mr. Rahimzadeh was not in the crosswalk at Almendral Avenue when he was struck.
Mr. Rahimzadeh was a 2001 graduate of Menlo-Atherton High School.
Police are investigating. "We're looking at the speed and that kind of stuff," Sgt. Hall said. "So far, we're not able to place (Mr. Rahimzadeh) in the crosswalk."
Mr. Rahimzadeh was struck hard enough to be thrown some distance from the site of the collision, Sgt. Hall said. There was "significant damage" to the Volvo, he said.
Police waited until the driver's parents were on the scene before interviewing her, and she was "absolutely cooperative" with police, Sgt. Hall said.
Southbound El Camino Real lanes were closed from 5th Street and northbound lanes were been reduced to one lane of travel.