It had to be a fox. A mink wouldn't be strong enough and a pine marten couldn't have climbed out with a full grown hen.
So! what next? He will be back, probably tomorrow night when he is hungry, they are highly predictable. I don't have a cage trap big enough, my rifle doesn't have a lamp fitted, it will have to be the shotgun.
At close range the .410 is just as deadly as a 12 bore.