Montreal police spokesman Daniel Fortier says investigators haven't established a link between the shootings but haven't ruled out the possibility they are connected.
In the most recent incident, a man in his thirties was found dead Saturday afternoon in a Montreal penthouse.
Police are also investigating a Friday evening shooting in an east-end mall parking lot that left one dead and another injured.
Investigators believe that shooting may have been gang related.
Another man was killed overnight while he was parking near his home in Laval, north of Montreal.