Sheriff's deputies were dispatched to 1135 Industrial Road around 8:40 p.m. when a GameStop clerk reported someone had entered the store, brandished a firearm and demanded money and merchandise, according to the sheriff's office.
The suspect left the store on foot in an unknown direction. An extensive search for the suspect did not locate him, sheriff's officials said.
The suspect is described as a black man, around 25 years old, roughly 5 foot 8 inches tall, 220 pounds with a stocky build and wearing a dark jacket, blue jeans, white athletic shoes, a white baseball hat and a white bandana over his face.
Sheriff's officials said he had a silver revolver handgun with wooden grips.
Anyone with information is urged to contact Detective Sgt. Gibbons at (650) 363-4063 or call an anonymous tip line at (800) 547-2700.