Click in the Eyewitness News Story Window above to watch surveillance video of the robbery.
The gunman removed a sawed off rifle from his pants leg, pointed at the clerk and ordered him to hand over cash from the register.
To make his point as the video rolls, the gunman puts a bullet into the rifle.
He fled with an unknown amount of cash, and the clerk was not hurt.
Anyone with information is urged to call the San Bernardino Police Department at (909) 384-5742.