The officer was among a group of community corrections officers who were doing their twice-annual firearms requalification at the Seattle Police Athletic Association shooting range, said DOC spokeswoman Norah West.
Somehow he accidentally discharged his firearm, shooting himself in the leg. He was taken to Harborview Medical Center, where he is listed in stable condition.
West said the officer is experienced and had previously requalified without incident.
The Department of Corrections is investigating the incident.