MONTREAL— Félix Rose was 7 years old when he realized that the gentle father he idolized had a secret past. “Your daddy killed someone,” his cousin told him during a family celebration, he recalled recently.

His father, Paul Rose had been a leader of a violent extremist group, the Front de Libération du Québec, or F.L.Q., that agitated for Quebec’s independence from Anglophone-dominated Canada. The elder Mr. Rose was convicted in 1971 of the group’s most notorious crime: the kidnapping and murder in October 1970 of a Quebec cabinet minister, Pierre Laporte. It was the first political assassination in Canada in more than a century.

Now, half a century later, the younger Mr. Rose, 33, has produced a documentary film about his family, “Les Rose,” that has been a surprise hit and sensation in Quebec, underlining how sensitive the events of that time remain, even decades later.

In making the film, Mr. Rose said, he was trying to understand what drove his father and uncle to violence. But some critics accused Mr. Rose of hagiography and historical revisionism, turning murderers into heroes.

“Every son wants to see their father as a hero, but ‘Les Rose’ is a whitewashing of history,” said Marc Cassivi, cultural commentator for La Presse, Canada’s leading French-language newspaper. “My fear is that young people will accept it as historic truth.”

From 1963 to 1970, the F.L.Q. unleashed more than 200 bombs and robberies, most of them in Montreal, including a bomb that tore through the Montreal Stock Exchange in 1969, injuring 27 people. At least nine people died in the group’s attacks, among them a 64-year-old secretary and a 15-year-old militant killed by his own explosive.

Violence escalated in October 1970, a period that became known as the “October crisis.” Days before it took Mr. Laporte hostage, the F.L.Q. kidnapped James Cross, a British diplomat, who was held for two months before being released.

Prime Minister Pierre Elliott Trudeau invoked the War Measures Act — the only time in Canadian history it was applied in peacetime. Armed soldiers patrolled the streets of Montreal, and hundreds of people were arrested without charges.