Not if you can show that you thought that "grievous bodily harm " was about to come to you. In Canada, contrary to popular belief, we do have the right to self defense, we can meet force with equal force, if you think that someone is going to kill you or your family, you can kill them first, its when you exceed the expected force that it gets sticky, ie you shoot them in the back as they are running away, once the threat is neutralized, you must back off.