Authorities released surveillance video of the June 23 incident. A man walked into the lobby of the Castaic Inn, pointed a gun at the clerk, ordered him into a restroom and warned him to stay there or he'll be shot.
The gunman grabbed an undisclosed amount of cash and got away.
The suspect was described as a man in his 20s, 5 feet 8 inches tall, weighing 170 pounds.
Anyone with information was urged to call the Los Angeles County Sheriff's Department.