The death of an inmate at the Maine State Prison in Warren is being investigated as a homicide. Police say Alan Powell died Tuesday night after being attacked by another inmate. Powell was serving a life sentence for killing a Waterville woman in 1989. Police say, Guy Hunnewell, 42, attacked Powell. Hunnewell is also a convicted murderer. Maine Department of Public Safety Spokesman Steve McCausland says Hunnewell is serving a 40 year sentence for stabbing to death his girlfriend in Fairfield in 1997.