I've seen this before. I never thought too much about it. I guess I just assumed the dog was playing. It seemed to me the dog was just bored and playing a game with itself ... oooooh, loooook, here comes the evil foot, sneaking up to steal my bone! Kind of like dogs will throw a toy for themselves, then run and attack it like it is trying to escape on its own.

One of my customers has a dog that will do this same thing on command, but with his tail instead of his foot. The man will say, "Mo, get your tail!" and Mo will ATTACK his own tail, with every much as apparent viciousness as the dog in this video does. Then his owner will say, "Did you kill it?" and the dog will instantly stop and be so proud of his job well done on a trick for his dad. It is completely hilarious, because we know what a nice man and a nice dog they are. Maybe that's the situation here.