Maine State Police are investigating the death of a Maine State Prison inmate, who was attacked by another inmate and died at the prison June 25.

Alan Powell, 57, was confirmed dead at 6:30 p.m. June 25. Powell had served 22 years of a life sentence for murder, said Department of Corrections spokesman Scott Fish.

Powell died after being attacked by inmate Guy Hunnewell, 42, while in an exercise area at the Warren prison, according to a news release from Maine Department of Public Safety spokesman Stephen McCausland.

An autopsy conducted June 27 by the Office of the Chief Medical Examiner has confirmed Powell’s death is a homicide. They have also determined the cause of death to be blunt force trauma to the head.

Powell was serving a life sentence for stabbing and strangling a Waterville woman in 1989. Hunnewell is serving a 40-year sentence for stabbing his girlfriend to death in Fairfield in 1997, according to the release.

Detectives went to the prison June 25 and conducted interviews with guards and inmates and the case will likely be presented to a Knox County grand jury in July, according to the release.

Hunnewell remains at the prison.