Léopold Dion was born on February 25, 1920, in Quebec, Canada.

Léopold Dion committed many serious crimes in Quebec in 1963. His first known sexual assault involved a young woman from Pont-Rouge. Dion and his brother attacked her on a railway track. They raped and stabbed her but left her alive. She survived, suffering from both physical and emotional injuries.

Dion's other victims were boys. He sexually abused 21 boys and killed four of them. He often pretended to be a photographer to lure them. His first murder victim was a 12-year-old boy named Guy Luckenuck. Guy was in Quebec City for clarinet lessons when Dion took him to a remote location. Without anyone knowing, Dion strangled Guy and buried him.

On May 5, 1963, Dion met two more boys, Alain Carrier and Michel Morel. He drove them to a dilapidated building. He pretended to play a game, tying Alain up. While he was dealing with Alain, he took Michel outside and asked him to undress. Dion then strangled Michel with a cord and went back to smother Alain.

Just a few weeks later, on May 26, 1963, he encountered another boy named Pierre Marquis. Dion again used his photographer act to lure Pierre. He took Pierre to a spot near Guy's grave and asked him to pose nude. When Pierre resisted, Dion strangled him.

Dion was arrested on May 27, 1963, after a boy who escaped his grasp described him to the police. After a month in custody, he confessed to his crimes and showed investigators where he buried the bodies of the children.

During his trial, Dion was defended by lawyer Guy Bertrand. He was only ultimately charged for the murder of Pierre Marquis due to a lack of evidence for the other cases. On April 10, 1964, he was sentenced to death, but his sentence was later changed to life imprisonment.

Léopold Dion died on November 17, 1972, in prison. He was stabbed by a fellow inmate, Normand Champagne. The inmate was later found not guilty of the crime due to insanity.