I have seen that too ghelmf2007 and as far as I know that it is not a glitch. Also with the dog attacking a dead body, maybe you saw it when the player being attacked were already in the ground that is why you can say that it is a dead body.
I saw in the game where there are two dogs fighting with each other. Both from different teams. Not only just between dogs but also Dogs Vs Squad Member. Haven't seen Squad Member VS Squad Member yet thou.
Dogs fighting is not new to me. I encountered this many times now. Regarding the dog attacking a dead body, the player must have been camping there or just laying there disguised as a dead body as a strategy that's why the dog attacked him.