Murderer admits killing killer cult leader MONCTON, New Brunswick, March 5 (UPI) -- A Canadian man was sentenced to life in prison Monday for killing killer cult leader Roch Theriault while they were both incarcerated. Matthew Gerrard MacDonald, a 60-year-old from Port au Port, Newfoundland and Labrador already serving life for murder, pleaded guilty to second-degree murder just ahead of his scheduled trial on first-degree murder charges in Theriault's death, the Canadian Broadcasting Corp. reported. MacDonald admitted killing Theriault in February 2011 while they were at Dorchester Penitentiary in New Brunswick. Authorities said a prison video showed MacDonald going into the 63-year-old Theriault's cell. "He [MacDonald] then is seen emerging and pulling a shank from Mr. Theriault's neck," prosecutor Anthony Allman told CBC News. And then he goes to the guards and says in rather cruder words than these that he just killed Mr. Theriault. Theriault's body was then found in his cell. Allman said MacDonald "had expressed some animosity towards Mr. Theriault" and his prior convictions for killing a woman and maiming another. He said some things about Mr. Theriault's prior record for convictions which involved girls and women. Theriault had led a cult from 1977 to 1989 in Quebec and Ontario, where he lived with eight women, his 26 children and several followers, the CBC said. He was convicted of killing one wife,Solange Boislard, by disemboweling her, and chopping off the right arm of another wife, Gabrielle Lavallee, with a chainsaw.