Very wrong
I won't just get mad and tell you you are a jerk or anything. It wouldn't be any productive for sure.
I also see you have a lot of supporters ... people leaving you comments about the fact there should be more students to kill, etc.etc.
That said, you do know you have a moral responsability over everything you do in your life ? I mean, no matter what you do or create, like a game about a shooting that just happened in a school, you will be responsible for the impacts it will have on other people.
So like I said, I am not mad about that game. Because, like many other people, I am smart enough to understand the difference about a small game on Newgrounds and a tragedy that happened in real life.
I am also sure it is your case, since I can't believe you created that to glorified violence or anything.
The big problem is, as I said earlier, that you will have moral responsability over the effect it might have on other people, let's say, more easily influenced people.
Those will take this possibly as a way to make violence ordinary or tolerable. You may even have an effect on some wakos, and this can't be good ...
Anyway, I do believe you should put your energy and your talent on something more productive, and more acceptable ... You know, that wouldn't make it lose any fun value cause of that.