There are plenty of reasons. Fear, lack of understanding, the generations gap, it explains a case of senseless violence. It's not merely one thing.
My own father once asked me why I still play video games. It was a sort of shocking question. I replied by asking him why he watched TV, movies, DVDs, and read books. Funny thing is that my mom agreed with me. But I do get it. He doesn't understand. To him, video games are a toy. They are "lesser" entertainment for children as they are something you "play". Adults don't "play".
It also helps explain why these sort of things happen. After all, random acts of violence never happened in the past. These are new things. Which is a lie, but it doesn't help that we have a 24 hour news cycle that has to find things to keep itself relevant. And that means you now hear about things that don't just happen a state over, but on the other side of the country and in every other country.
Why do people think the US Government perpetrated 9/11? Because it makes them feel better. I mean there's no way terrorists could have done that. That's the sort of thing that only a huge government conspiracy could pull off. That would be like some maniac walking into a school and killing children with a gun, knife, or bombs. That just couldn't happen. Not normally, right?
And in the case of school violence, who is a better scapegoat than "the other"? After all, "normal people" don't play violent video games.
Geth Reich (Yakob) said:
Because whenever I rage-quit COD: Ghosts online, I go outside and punch a random neighbour.
I guess that explains the Knockout Game.