The robbery was reported at about 1:10 p.m. Saturday at a bank in the 200 block of West Portal Avenue, according to police.
The suspect entered the bank, approached a teller and demanded cash. The teller, a 22-year-old woman, gave him a small amount of cash, but he demanded all her cash or else he said he would shoot her, police said.
The victim gave the suspect more money, and he fled in a maroon, four-door Toyota Corolla. The suspect is described only as a black man between 25 and 30 years old, according to police.
The victim was not injured in the robbery.