It is for national security reasons. One of the perpetrators over stayed a student visa by a year. That individual also appeared in a promotional video with a visa providing company which the university stated it has no affiliation with. Student visa are conditional and requirements must be met or you will be deported. This is common in many countries.
The article emphasises this idea hence why the people accused of state sanctioned murder are having their visa/background scrutinised.
It's an election year and I haven't heard a damn thing out of jagmeet Singh except when this issue comes up. It's clear he only cares about the south Indian community, and doesn't want to be the PM of Canada