Dion was born in 1921 and had been convicted of a large number of rapes, the figure given is twenty-one, and had served substantial prison terms before 1963.
Between April and May 1963 he abducted and killed four boys in the Quebec City area: Guy Luckenuck, twelve; Alain Carrier, eight; Michel Morel, ten; and Pierre Marquis, thirteen. He approached them saying he was a photographer, took them to a wooded area, assaulted them and strangled or smothered them. The Quebec press called him the monster of Pont-Rouge.
He was arrested on May 27, 1963 and led police to the bodies.
He was convicted and sentenced to death on April 10, 1964. The sentence was commuted to life imprisonment, Canada having effectively stopped executing by that point and abolishing capital punishment in 1976. On November 17, 1972 he was stabbed to death in prison by another inmate, Normand Champagne.
The case is remembered in Quebec partly for the killings and partly for what preceded them: a man with a record of twenty-one rapes had been released, and four boys died within weeks.