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OKLAHOMA CITY, Okla. — A convicted child killer was strangled to death in prison, according to the Associated Press, citing state authorities.

Anthony Palma died from “ligature strangulation and blunt force trauma to the head” on Jan. 11, according to a report released Tuesday.

Palma died in his cell at the Oklahoma State Penitentiary in McAlester, Okla. He was found unresponsive during a routine security check, could not be revived and was pronounced dead. Palma’s cellmate was also serving a life sentence for first-degree murder.

Palma was serving life without parole for the murder of 8-year-old Kirsten Hatfield, who was abducted from her Midwest City home in 1997.

He had lived two doors down from the Hatfield family and was arrested for the cold case murder in 2015 after a DNA sample matched evidence from the investigation into the girl’s abduction.

How the cold case was solved

In 2015, police said authorities had been led to Palma after a new investigator assigned to Hatfield’s case in 2014 realized the FBI or the Oklahoma State Bureau of Investigation had never tested some of the evidence.

Using DNA technology more advanced than it was in 1997, lab technicians discovered blood from the window sill and the girl’s underwear came from an unknown male, Midwest City Police Chief Brandon Clabes said in 2015. Investigators ran that DNA through a national database and didn’t find a match.

Authorities then tracked down about 10 men who’d previously been questioned and asked for DNA samples, Clabes said.

One of them was Palma, who lived just two doors down from the Hatfield house and had been interviewed twice in 1997, Clabes said.

His sample matched the DNA on the underwear and the window sill, the chief said.

CNN contributed to this report.