I know it goes against the grain, but if people refrained from feeding and leaving scraps accessible to foxes they wouldn't breed so much and would eventually retract to the bush.
Just to emphasise Dr B's point - sweet little pet doggiewogs soon revert to ancestral type and often inflict this kind of damage. Tambo - do you know beyond doubt that a fox did this? Just a thought.
Of course, we don't know whether a fox found the animal dead or alive. I have dumped deer, (killed, incidentally, by my dogs), on the farm and the foxes soon dismantled the corpse.
Nature is cruel by our standards. I have to go along with those who see this as natural, if unfortunate. At least it had half a rabbit before it decided not to overeat. Perhaps it'll bring a mate next kill and not waste any.