Typically Liberals will claim terrorist attacks are a result of mental illness and not jihad or Islamic-inspired terrorism. I think Trudeau will do the same here.
When a Muslim immigrant commits an act of terror, its bad politically for Trudeau and good for Trump. That's pretty obvious given their policy isn't it? Trudeau will have to explain why we're safe allowing in more immigrants and Trump can point to it as an example of why we should control immigration from terrorist hot beds for closely.
As for your statement about whites being responsible for the majority of shootings, I certainly would expect that to be the case given that about 80% of Canadians are white. However, last I heard the RCMP and other police forces banned race-based statistics so I'm not sure how you could make that claim with any certainty. Source?