The slaying of Nicolo Rizzuto, considered the Godfather of the most powerful criminal group Canada has ever known, marks the end of an era and possibly the return of Calabrian rivals, experts say.

The 86-year-old don was shot dead at his Montreal mansion late on Wednesday. According to police, the killer shot him from outside the home and then disappeared into the night without a trace.

The apparent professional hit caps a series of slayings of Sicilian mobsters and attacks against a crime family that has controlled the city’s underworld for three decades.

The aim probably of a rival clan, according to crime writer Andre Noel, was the systematic elimination of the Rizzutos. “My first reaction is that this marks the return of the Calabrians,” he speculated.

It was by supplanting the Calabrians and murdering mob boss Paolo Violi in 1978 that the Rizzutos took control of the Montreal underworld.

According to Noel, Calabrian clans had recently launched an “offensive” against Sicilian clans in Europe and won. “I suspect the same thing is happening here,” he said.

There may also be an element of revenge: the two sons of Paolo Violi who were just children at the time of his death have grown up and could have met up with young Sicilians unhappy with the Rizzuto’s rule.