KGO-TV said the unidentified youth was described by relatives and workers at the ARCO gas station where the shooting occurred late Tuesday as 14 or 15 years old.
Police said a lone officer made contact with the boy about 9 p.m. and was talking to him at "interview distance" when he suddenly felt he was in danger, pulled his gun and shot the boy, the San Jose Mercury News reported. The youth was taken to San Francisco General Hospital with life-threatening injuries and was later pronounced dead.
The newspaper reported police said a gun believed to have been carried by the boy was found at the scene. It had not been fired.
It wasn't known what prompted the interaction between the victim and the officer.
The officer, who was not hurt, was being interviewed by investigators.