Montana prisoner with history of mental illness dies after disemboweling himself at state prison Ashley Nerbovig View Comments A man with a history of mental illness and self-harm died May 23 after he disemboweled himself while in custody at the Montana State Prison. Shaun Duncan Morrison, 39, died from a self-inflicted open wound to his stomach wall, according to his death certificate. Morrison caused the injury to himself on May 19. He lived for four days before dying from his injuries as well as sepsis while receiving treatment at Benefis Healthcare System in Great Falls. Morrison was serving a life sentence without the possibility of parole after he killed another inmate at the prison in 2011. Morrison was part of a group of prisoners who were involved in a lawsuit against the Montana Department of Corrections and the state prison concerning the treatment of incarcerated people with mental illness. Prior to that, he was incarcerated for attack a police officer, records show.