Douglas County authorities are looking for the gunman who killed a convenience store clerk during an armed robbery around 11 p.m. Monday.

Chief Deputy Stan Copeland of the Douglas County Sheriff's Office, said Tuesday Maryann Humphrey was shot and killed when she tried to fight off an armed man demanding money at the Circle K convenience store on West Stewart Mill Road.

Copeland said surveillance cameras show a man with a slight build who was probably in his  late teens or early 20s. The gunman had concealed his face by draping  a towel with an American flag design on it around his head and face.