MONCTON, N.B. - A 60-year-old man serving time for two deaths -- including that of a fellow inmate -- has been charged with murder in the slaying of a former cult leader inside a New Brunswick prison.

Matthew MacDonald of Port au Port, N.L., is charged with first-degree murder in the death of Roch Theriault.

Investigators say Theriault was found dead near his cell at a penitentiary in Dorchester, N.B., on Feb. 26.

They say the 63-year-old was involved in an altercation with another inmate and died from his injuries.

Theriault founded and led a notorious sect in the 1980s.

Theriault was sentenced to life in prison in 1993 for the murder of his wife, Solange Boilard, who was killed with a kitchen knife as part of a cult ritual.

The Correctional Service of Canada says MacDonald was serving time at the penitentiary for the second-degree murder of a taxi driver in British Columbia in 1985 and manslaughter of another inmate years later.