Sorry for your loss. Your description suggests Mink, to me: http://dnr.state.il.us/orc/wildlife/furbearers/mink.htm
Was your screening .5" hardware cloth? We use double layered over windows and venting secured to frames/walls with wood screws through 1.5" dia. washers (raccoon heavy, here). If you have a live trap you could place that in coop and cover all but the door with an old towel or the like (makes it look more like a den/hollowed section of dead tree) and use some fresh/bloody meat. This setup might be a starting point: https://www.backyardchickens.com/forum/viewtopic.php?pid=2754962#p2754962
Might put together a weasel box (as has been mentioned) : http://www.youtube.com/watch?v=epykoVZ_ufU
Hope you get whatever it is.
Good luck!
Was your screening .5" hardware cloth? We use double layered over windows and venting secured to frames/walls with wood screws through 1.5" dia. washers (raccoon heavy, here). If you have a live trap you could place that in coop and cover all but the door with an old towel or the like (makes it look more like a den/hollowed section of dead tree) and use some fresh/bloody meat. This setup might be a starting point: https://www.backyardchickens.com/forum/viewtopic.php?pid=2754962#p2754962
Might put together a weasel box (as has been mentioned) : http://www.youtube.com/watch?v=epykoVZ_ufU
Hope you get whatever it is.
Good luck!