You do realize that the US are the only country in the world where this kind of things happen?
In other "rich" countries, we don't hear about mass shootings. Ever wondered why?
But yeah, the US is the land of freedom...and nutjobs.

That is not an entirely accurate statement. Mass shootings do happen in other "rich" countries, but with much less frequency. I mean according to this Wikipedia article,
3 have happened this year in Canada.
https://en.wikipedia.org/wiki/List_of_massacres_in_Canada If you are not "hearing" about it, maybe you are not paying enough attention.
Only 2 actually, 1 of the ones in your link used a van, no firearms were used, the officer that responded was a real hero as he was able to apprehend the sick fuck without firing any shots.
Per capita mass shootings in the USA are way higher. In order to compare the actual numbers you have to define "mass shooting" but firearm homicides are 8-10X higher per capita in the US than Canada and it's higher than that compared to a lot of other "westernized" countries.
There are hundreds of millions of people around the world that have looked at the stats and concluded very quickly that military weapons in the hands of civilians leads to only one thing, less safety for the entire country...