"It was a surprise to me," says Dale Manuel, Jefferson County Commissioner. "It happened outside of the regular working day, I had not anticipated that happening on Friday evening at about 7:30."
Shirley admitted to kicking a bank robber suspect in the head, at least five times, breaking his nose and fracturing other bones.
Shirley faces up to ten years in prison and a fine of $250,000.
County officials say they don't know if the resignation has anything to do with the case. Now they're left scrambling around trying to figure out the next step.
"We're making every effort to make sure this doesn't any impact on the residents of Jefferson County and the ability to provide for the public safety," says Manuel.
Chief Jones has taken on the responsibilities of sheriff and will be managing the department until a new sheriff is appointed.
County commissioners will be accepting applications for the sheriff position for the next two weeks before making a decision.
"We're going to try to make this move as smoothly and as transparently as we possibly can," says Manuel. "We're going to make sure everybody has the chance to put their application in who will meet the qualifications."
Shirley will remain free pending sentencing but he has been placed on home confinement. He was also forced to turn over all of his firearms.
Shirley's sentencing will be set in the next 60 to 90 days.