Deputies were dispatched at 12:03 p.m. Thursday to the Chase Bank branch at 26791 Portola Parkway, said Sgt. Frank Gonzalez of the Orange County Sheriff's Department.
The suspect fired a round near the foot of a teller, Gonzalez said. The teller was not struck by the gunfire.
The suspect was only described as wearing a bucket hat, black mask, yellow sweatshirt and tan pants.
The robber made off with about $31,000, he said.