Just lost half my flock over a week period to an Ermine (Weasel). I kept closing holes and it kept getting in daily. The last attack I was actually standing there, had time to get my gun and load it, and missed the little bastard by centimeters. It had even begun to tear off shake shingles from the coop exterior but thankfully its solid behind that. Figured out finally I had a hole in my run apron under the ground where moles had burrowed in. Point is, you've got an Ermine more than likely. Close and cover every inch of your duck house with hardware cloth because it won't stop until their either gone or all dead. And they will kill during the hours of daylight if the opportunity presents itself. Sorry for your loss.