For their own protection my chickens and cats have separate enclosed runs. My cats have runs and catios outdoors but live indoors 24/7 so they can't harm anything.Sorry for your loss!
Fortunately most cats aren't motivated to kill anything big as a chicken.They prefer small game. Barn cats raised around chickens actually bond with them and protect them.Small predators such as weasels are less inclined to come around if you have barn cats