A man serving a 45-year sentence for murder has been charged in another killing, this time a fellow prisoner who was serving life for a double murder.

Maine State Police notified Frank Higgins, 49, that he was indicted on a charge of murder by the Knox County Grand Jury.

Higgins, convicted in the 1999 killing of a woman in Kenduskeag, is charged with killing Lloyd Millett. Millett was assaulted May 24 at Maine State Prison in Warren and died June 7.

Millett was convicted of strangling two women in 1995, Terrie Lizotte, 39, of Canton, and Rachelle Anne Williams, 33, of Gorham, N.H.

Williams’ body was found in a field near a Lewiston hotel, and Lizotte’s body was found hours later in a closet in Millett’s trailer.

Higgins will make his initial appearance in Knox County Superior Court next week.