In China on the same day a dude stabbed 22 kids, not gun, knife, when a psycho wants to hurt, they will hurt, regardless of the weapon, granted controlling access to weapons MIGHT help, it is not the solution and it is not the problem at hand.
In Costa Rica you have to take shooting lessons and take a mental health assessment in order to carry a weapon, seems like a wonderful idea right? keeps guns off crazies right? NO, there's always some low life asshole professional that will do a half assed job or that will overcharge and give the permit anyway, and even if an ideal society everyone was righteous and that didnt happen, there are still other ways, taking it from a parent (like in this case) from a neighbor, stealing it, buying it off the streets, etc again, when a wacko wants to hurt, they will, period.