What a sad sad day.
Even countries with gun control have instances like this (but they're arguably less frequent), and some countries with lots of guns have almost no problems like this at all (Switzerland for instance).
Just trying to imagine dropping a grade school kid off at school to find them dead in the afternoon from an insane thing like this I find that I can't do it, it is just too far from what I can still imagine. And I have a pretty rich imagination...
This world could be so nice, why does it have to be such a crappy place?
When you have a population size of 300 million you're going to get a lot more outliers (crazy people) than if you have a population of 7 million. Statistically, you will also have crazier people.