WARREN, Maine — An autopsy conducted Thursday by the state medical examiner’s office has determined that the cause of death of a Maine State Prison inmate Tuesday night was homicide.

The autopsy also determined that Alan D. Powell, 57, died as the result of blunt force trauma to the head, Maine State Police

Lt. Christopher Coleman said Thursday.

The case will be presented to the Knox County Grand Jury during the July session.

No further details, including whether a weapon was used, are being released at this time, Coleman said.

Powell, a convicted murderer, died after he was attacked by another inmate, who also was serving a prison sentence for murder, in an exercise area at the prison, Stephen McCausland, spokesman for the Department of Public Safety, said in a press release issued Wednesday.

Powell was killed at approximately 6:30 p.m. He had served approximately 22 years of a life sentence for murder, Scott Fish, Corrections Department director of special projects, said Wednesday morning.

Powell was attacked by 42-year-old Guy E. Hunnewell III, who is serving a 40-year sentence for stabbing to death his girlfriend in Fairfield in 1997, according to McCausland.

Hunnewell was sentenced in 1999 in Somerset County Superior Court to 40 years in jail for killing Stephanie Gilliland, 20, of Benton in December 1997 at his Fairfield apartment, according to Bangor Daily News coverage of the trial.

Gilliland, who was Hunnewell’s estranged girlfriend, was stabbed more than 21 times.

Hunnewell also was indicted by the Knox County Superior Court grand jury in March 2003 for allegedly assaulting another inmate with a shank, the BDN archives state.

Hunnewell remains at the prison, which was visited by detectives Tuesday night who conducted interviews with guards and inmates.

Powell was convicted of murder and gross sexual misconduct in Kennebec County Superior Court in 1991 for the stabbing and strangulation of Martha Daigle, 64, in her Waterville home on June 29, 1989. He was sentenced to life for the murder and a concurrent 20-year sentence for the sexual misconduct.