 On 8 September 1997, Gagné and a fellow biker, Paul "Fon Fon" Fontaine, gunned down the prison guard Pierre Rondeau.During the attack on a prison van carrying prisoners from Rivière-des-Prairies prison to court on the morning of 8 September 1997, Gagné and Fontaine began to shoot up the front seats of the van with their handguns, killing Pierre Rondeau and badly wounding another guard Robert Corriveau, who was critically injured but survived.Only the fact that Gagné's gun jammed saved Corriveau's life while Fontaine decided that since Corriveau was already badly bleeding he would die before an ambulance arrived.