The Canadian PM is assassinated when in a meeting with the US and Mexican presidents at a landmark summit in Mexico. That's how Ghost Recon: Advanced Warfighter, the highly anticipated game begins who demo was released a few days back.

No, Canadian PM Stephen Harper didn't comment on the game that begins with the assassination of the figure that he is.
Anyway, a bit of more info on this. You will actually never get to see the killing. Actually, the assassination part sets up the game's storyline.
French developers Ubisoft developed the game and said that the Canadians shouldn't take offence to the assassination.
After all, it's a game only!