40 year old Cletus Armell disappeared after leaving a residential treatment facility on a shopping pass.
Armell is 5 feet 11 inches tall, 190 pounds, with black hair and brown eyes.
Armell was halfway through a 15 year sentence for 2nd Degree Robbery and Going Armed with Intent.
He left his work release yesterday and never came back.
If you've seen him you should call Sioux City Police or the Woodbury County Sheriff's Office.
Woodbury County Sheriff's Office: 712-279-6010