Was this a full grown rooster or a cockerel? I would be getting a necropsy ASAP if available in your area, as it could be something that is present in all of your flock and not presenting symptoms yet in the rest. Check your husbandry, poops, and flock over throughly. Many chicken illnesses are highly contagious. And no offense, but I really don’t think there is anything funny about losing a bird ever, to a predator or illness, and regardless of weather the bird was destined for food, re-homing, or going to be a full permanent member of your flock. Just to everyone making light and brushing off the situation.