Gordon Harold Williams, 49, of Knoxville was arrested Tuesday and charged with a Monday BB&T bank robbery.
Williams has entered a plea of not guilty in court, but officials say an affidavit on file claims he admitted to robbing the bank when he was arrested.
They say the affidavit also says he confessed to having an explosive device in a backpack during the robbery.
Authorities are searching for the person who robbed a BB&T Monday afternoon.
Around 1:30 pm Monday, the suspect entered the BB&T Bank located at 7108 Maynardville Pike in Knoxville. There the the Knox County Sheriff's Department said the suspect allegedly demanded money and then fled the scene.
Officers said witnesses described the suspect as a white male between his late 50s and early 60s. They said he is approximately 6' to 6'2'' tall and weighs approximately between 275 to 300 pounds.
Witnesses said the suspect was wearing blue jeans and a white t-shirt underneath a long-sleeved, multi-colored, pullover shirt with horizontal stripes. They said he was wearing sunglasses and a baseball cap.
A release from the Knox County stated that the suspect stole an undetermined amount of money.
Authorities said they are offering a reward for any information leading to the suspect's arrest.
Anyone with information is asked to call the FBI at 865-544-0751 or the Knox County Sheriffs Department at 865-215-2243.