SUPERIOR, WI (KDAL) - An inmate in the Douglas County jail died Friday after suffering a catastrophic medical event. According to the Douglas County Sheriff's Office, 37 year old Clifton G. Walker told other inmates he was not feeling well and went to lie down. Later he was found to be in distress and stopped breathing. Efforts to revive him by Corrections Officers were unsuccessful and Walker was pronounced dead. An autopsy showed that he died of massive internal bleeding due to a perforated ulcer that ruptured an artery in the stomach lining. The incident remains under investigation by the Douglas County Sheriff's Office and the Wisconsin Department of Corrections.