The director may have cut a scene out of the movie, in which Bill gets in a fight with the dog.

I suspect this because the scene where Bill is on the "night shift" ends abruptly with him offering the dog some chocolate. The next scene he is waking everyone up. When he is confronted with the dog, it jumps up and barks. Bill raises his hands in a Karate move position, (one of his hands has a bandage on it that wasn't there the night before...) after seeing this Karate imitation, the dog whimpers and runs off. Could there have been a confrontation that night?