Photos from a surveillance camera show the robber wearing a black ski mask and blue jeans. The suspect also arries a black semi-automatic handgun.
The FBI says the man has a distinctive tattoo on the back of his left hand.
Authorities believe the robber is a white or a light-skinned black man, around 5'10" tall weighing 180 pounds.
Anyone with information is urged to call the FBI or Concord Police.