Angry kitty growling because we ran out of snacks

Fear is the fundamental motivator for a cat's angry or aggressive behavior. Cats, unlike dogs, are not as tamed and can readily revert to their natural condition. This indicates that cats are still one step away from being a wild animal, and many wild animals are always on the lookout for danger, which includes a fear of humans. Strangers are at the top of the list for creating fear, simply because a cat doesn't have any.