Why did Dana choke Roy?

Dana Matherson is the resident bully at Trace Middle School. As Roy is the new kid, he immediately becomes a soft target for Dana, and so he picks on him relentlessly. One day on the school bus Roy looks out the window and sees a barefoot boy running through the streets. Roy is intrigued by this strange creature, who in actual fact is Mullet Fingers, as he'll eventually discover. In fact, Roy is so intrigued that he tries to get off the bus to investigate.
However, Dana won't let him. Bullying Roy on the school bus is pretty much the highlight of his day, and he's damned if he's going to be deprived of his fun. So he grabs hold of Roy and smashes his face against the window. Just for good measure he starts choking him too. Thankfully, Roy manages to escape Dana's evil clutches by swinging round and breaking his nose. But it won't be the last run-in that Roy has with this thoroughly nasty piece of work.