An inmate serving life at an Oklahoma prison for murdering an eight-year-old was found dead in his cell Friday, the Oklahoma Department of Corrections said.

A corrections officer doing a security check at the Oklahoma State Penitentiary discovered Anthony Joseph Palma, 59, unresponsive in his cell around 7:30 p.m. on Friday. Medical staff attempted to revive Palma but pronounced him dead at 8:55 p.m.

Officials did not release details about how he died but believe “his cellmate” was the one who killed him, according to the corrections department.

Palma was sentenced to life in prison without parole 13 months ago for murdering Kristen Hatfield, who had been abducted from her home in 1997.

Palma lived two houses away from the Hatfield family, and had been arrested in 2015 in connection with Kristen’s cold case murder after DNA testing determined his sample matched evidence linked to Kristen’s abduction.

The victim’s family told the Oklahoman in 2017 that they forgave Palma and said they would be keeping him in their prayers.

“I pray that you someday realize God’s love for you,” Shannon Hazen, the girl’s mother, said.