Griefing. The act of undermining another's online gaming experience. It's usually a dirty word, one associated with cretins and assholes. Yet when applied to the right target, it can also be associated with great things.
This is Garry's Mod. It's a PC "game" based on Valve's Source Engine, and lets people run around just... doing stuff with stuff to their heart's content. Most of the time that means building incredible contraptions, but in this case, it means tormenting a very angry young boy by locking him inside a glass prison.
Don't ask yourself "why didn't the kid just reset his connection?" Because if he had, we wouldn't have been able to watch this, and our days would all have been a little darker.