Thanks, everyone - we've spent a lot of time locking down all our coops and runs so that nothing can ever get in, just for a door to be left open a bit past dark and this to happen... this summer we had a whole quartet of raccoons breaking into one of the runs nightly through the CEILING to feast on chicken food, luckily not the chickens themselves, and we had the whole thing re-roofed to stop it. I've been forgiving with having possums around up until this point, but no longer, I guess! Unfortunate that this is what it took to learn that lesson. ): Thank you for the condolences.