It's unlikely that your rabbit killed your other rabbit. More than likely, Dumplin' died of a natural cause, and a frantic Stewie groomed him to baldness. Even if he had ripped off all his fur while they were fighting, that wouldn't cause him to die.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry