The call came in at 12:58 a.m., and responding officers located the car in question parked at a Quik Stop convenience store at 1001 MacArthur Blvd.
Officers determined that the driver had been drinking, and they could smell marijuana wafting from inside the passenger compartment, according to police.
They then learned that the driver was on parole, and officers searched the car. They found a loaded 9mm Luger handgun under the front passenger seat, according to police.
The three people in the car -- San Francisco residents Alexis Mathis, 30, and Royce Montgomery Jr., 21, and San Lorenzo resident Jeremy Mathis, 20 -- were arrested on suspicion of possessing a loaded firearm.