I'm very sorry. It's a terrible tragedy.
I was a witness (about 30 meters away) to a school shooting my second week of 6th grade, and I have to say, it changed my view on people in general forever...for better or worse, I'm unsure.
The best thing you can do is hope and pray that the surviving victims and your cousin make it out alive. Other than that, console your family. Good luck, Jack.
PS- if you're kidding, fuck you