Donald Lavoie was born on May 21, 1942, in Chicoutimi, Quebec, Canada. He was one of three siblings, and at a young age, he and his brothers were placed in an orphanage by their parents. The specific reasons for this family separation remain unclear. Despite his challenging upbringing, Lavoie claimed he was a smart student who did well in school. However, by his teenage years, he had already drifted into criminal activity.

His early offenses included breaking and entering, along with convenience store robberies. These petty crimes marked the beginning of a deeper descent into organized crime. Seeking bigger opportunities, Lavoie moved to Montreal, where his life would take a violent and irreversible turn.

After relocating to Montreal in the early 1970s, Lavoie became associated with the infamous Dubois Gang — a powerful and nearly untouchable criminal organization led by the Dubois brothers. It didn’t take long for Lavoie to gain their trust. With his growing reputation for being ruthless and efficient, he became the gang’s top hitman. Over a period of ten to twelve years, he worked closely with the Dubois brothers, carrying out hits and assisting in various other criminal operations.

According to his own confessions, Lavoie personally murdered at least 15 individuals, all by gunshot. Beyond his own killings, he also had firsthand knowledge of at least 27 murders committed by the gang and served as a close witness to their internal operations.

His violent career came to an abrupt end in 1982. Lavoie overheard Claude Dubois and another gang member conspiring to kill him. Realizing his life was in immediate danger, he escaped by sliding down a laundry chute and remained hidden until he could contact the authorities. That event forced Lavoie to turn informant. He contacted the police and agreed to cooperate in exchange for protection.

His testimony in 1982 was a major breakthrough for Montreal law enforcement, who had long struggled to infiltrate the Dubois Gang. Lavoie’s insider knowledge led to the conviction of multiple gang members, including Claude Dubois, who was sentenced to life in prison for murder. Lavoie also testified against Adrien Dubois, claiming he had driven him to a murder scene.

Despite admitting to multiple homicides, Lavoie was never formally charged for any of the murders he confessed to. He served time in a penitentiary, though the exact duration remains unclear. He was eventually placed in Canada’s Witness Protection Program to ensure his safety.

Lavoie's testimony helped dismantle the Dubois Gang permanently. He provided detailed information not just on murders, but on the inner workings of the criminal enterprise. His cooperation made him one of the most effective police informants in Canadian organized crime history.

In his post-crime life, Lavoie has lived quietly in the Laurentians, Quebec, under government protection. His story resurfaced in the public spotlight with the 2023 release of the film Dusk for a Hitman (Crépuscule pour un tueur), where actor Éric Bruneau portrayed him.