Yes. The main thing is that prevention is more efficient.
That being said, it depends on the objective of the government. If the objective is to reduce mass shootings and perhaps terrorism too.... I would say that what the government calls at the moment “military-style assault rifles” are the preferred weapons used by mass shooters. If you prefer, self-loading weapons like semi-automatic pistols or rifles are the most used weapons to do mass shootings. If the government wants to reduce mass shootings, reducing the accessibility of those weapons is a way.
That being said, I think you are right. As a society, we have to address the causes of violence in Canadian cities and issues of mental health. I agree. However, again, it depends on the objective of the government.