SIOUX FALLS, S.D. (MITCHELLNOW) State prison officials say 36-year-old prison offender Leo Plenty Arrows died following what appears to be a suicide. Plenty Arrows was found unresponsive in his cell at the Jameson Annex in Sioux Falls on June 20th. He was taken to a local hospital, where he was later pronounced dead. At the time of his death, Plenty Arrows was serving time for simple assault on law enforcement in Pennington County. Authorities say the incident is under investigation.