The gun-grabbing politician, the one working overtime to disarm you, your neighbor and your kids' teachers, the one who only feels secure when you are a victim, that is who is to blame for the Parkland shooting as well as so many others.
NRA is his enemy and, whether you want to believe it or not, NRA is your defender. NRA lobbies to keep government from encroaching on your God-given right to protect yourself and your family. The Constitution forbids Government encroachment on that right.
If you need to hate someone, hate the politician that made you unsafe. Better yet, get them the hell out of their position of power over you.