A well regulated militia being necessary to the security of a free State, the right of the People to keep and bear arms shall not be infringed.
Yes, on the subject of alleged perpetrator(s) the current situation is lone wolf in custody, scattered political interests generally more to right than left but confusing mixture of interests, lingering questions outside of official media/political circles about role of possible other suspect(s) whose roles changed to witness, one thing known is that the suspect belonged to a gun club and had some hunting experience although was also a bird-watcher.
By the way, from Quebec City one would not cross a river at the Maine border that would be folks from New Brunswick. In fact, I would think if I were looking to cross the border to shop for anything, while Maine is a bit closer, I would head to St Johnsbury, VT as the nearest large town. You would have to drive all the way through Maine to reach any populated areas.
Criminal gangs in Canada have lots of high powered weapons, the black market for them appears to be robust.