Police arrested a South Carolina man Thursday shortly after the robbery of a bank in the South End in which a teller was threatened with a bomb, authorities said. The robber passed a note to a bank teller at Commerce Bank on Washington Street stating that he had a bomb, said a statement from Boston police. The robber stole an undetermined amount of money and fled on foot. Police officers spotted Terrell B. Anderson, 20, who matched the robber’s description, near 500 Harrison Ave., and also found a bag full of cash underneath a nearby car, the statement said. Anderson was arrested and charged with armed robbery of a bank.