It was probably an urban fox which had been released into the countryside. Some people think this is a kind act, but in reality they starve to death because they aren't used to hunting as rural foxes do. The farmers round here are able to pick off the urban foxes quite easily with rifles because they don't run away when humans or vehicles come near.
Rural foxes on the other hand are vicious animals which kill for fun - when all chicken bodies and heads are accounted for after a massacre, you can't say the fox was hungry.