Cat kills chicken...

...we think. We are fairly certain my aunt's neutered cat killed one of the chickens. Is there any way to stop a cat for doing that?? Have you ever heard of a domestic cat doing that?? He isn't hungry and he is pretty independent. I've never heard of such a thing and don't have a clue how to stop other than finding the cat a new home. I hope someone here will be able to help us. Thanks!!!