I'm normally not one to champion extreme prison sentences, but 5 years really doesn't seem like enough in this case. I remember seeing the video, and it's clear that the kid has some major issues that aren't going to be solved by a few years of prison time. He kept attacking her after it was clear she was already unconscious; whether it's over a video game or not, that is not healthy behavior. Most people know, even in high-stress self defense situations, that once somebody is unconscious, you don't keep attacking them. He had no issue attacking somebody he knew was completely defenseless. That's sociopathic behavior.
Most people don't come out as better people because prison does nothing to actually rehabilitate people, but I can't imagine this doesn't make him even worse. He needs to be hospitalized, otherwise in 5 years we'll probably see his name in the news again.