We also know this to be true because he already had friends there! They were the ones filming and egging him on. Casey only had one person step up to help him and even that was after the fact.
Casey has been picked on since he started going to that school. He's big so they pick on him. He holds his temper so they think he's weak. He's sensitive and cries because he thinks everyone hates him...so they see this as weakness and pick on him more. There are other videos of him getting picked on by other kids his own age. The Rat was trying to get in with the older crowd and that Casey was the chosen target because it had been done so many times before. Casey felt alone at his school. His parents (well, his dad anyway - nothing has been heard from his mother) have been unable to get anything accomplished.
What exactly was he supposed to do? Walk away? You can't just walk away from a mass of bullies. They want a fight and they want to show their power over those they perceive as weaker. Casey had been the target of these jackals for years and he finally did something about it. It can be notes that he did not swing, he did not try and hit, he did not try and kick. He picked the kid up and threw him down. Casey does not know how to fight so he did the first thing that came into his mind.
According to the news, Casey's dad is glad he got the 4 day suspension - he's afraid of what the bully patrol will do to his son when he gets back in school.
I, for one, am glad that anonymous got in on this. Let the kids mess with Casey when he returns. It'll get out. They want to pick a fight? They'll get one.