The answer is that William Robert Scully, 35, was blown up in the basement apartment at 5575 St. James St. W., an apartment in which anti-separatist newspaper clippings had been taped to the walls.
The presumption being that he had been amassing the explosives in order to perpetrate a political attack on the then-Rene Levesque-led Parti Quebecois government of the day.
Upstairs neighbours Gloria Fiorentino, then 17, said that she didn't know Scully much and he hardly talked to anybody and seemed depressed.
The bomb was powerful and killed Scully instantly but a neighbour named Donald Ouellette, then 25, still rushed to his aid, putting out his flaming hair.
Coolopolis reader Mark F commented on this site that he knew the guy a little and he speculated that it might have been a suicide. Another neighbour I contacted through Facebook lived two doors down at the time but had no other insight into the affair other than that it caused a stir at the time.