Notorious killer and former cult leader Roch Thériault has died of injuries suffered in an altercation Saturday at Dorchester Penitentiary in New Brunswick, RCMP say.

Cult leader Roch Thériault, shown in a 1981 photo, was serving a life sentence at Dorchester Penitentiary in New Brunswick. (Canadian Press)The Quebec-born Thériault, 63, was serving a life sentence for murdering one woman and maiming another.

A 59-year-old inmate at Dorchester has been arrested in connection with Thériault's death, which police are calling a homicide.

Correctional services spokesperson Étienne Chiasson said the penitentiary is co-operating with the RCMP and coroner's investigation.

"The safety of the inmates, of our staff and the public are paramount for CSC," said Chiasson.

"That's why in such events under any circumstances and no matter who the inmate is or the victim, we take that seriously and it's important to us to investigate and find out what happened."

The Correctional Service of Canada is also investigating the incident.

Thériault led a bizarre cult from 1977 to 1989, first in Ste-Marie de Beauce, Que., then in Gaspé, Que., and then Burnt River, Ont., where he lived with eight women, his 26 children and several followers.

He killed his wife and cult member Solange Boislard by disembowelling her, and chopped off the right arm of another commune wife, Gabrielle Lavallee with a chainsaw.

In 1993, Thériault was sentenced to life in prison and was put in Dorchester, a medium security prison southeast of Moncton that houses about 440 inmates.

Dorchester Penitentiary is under total lockdown for the homicide investigation, police said.