I'm also glad you have dispatched the opossum, but not because it "might" have rabies. I don't think that's the situation at all - as another poster said, it's perfectly normal 'possum behavior.
I had a young one take refuge in one of my coops where nobody sleeps. It's an A-Frame and they mostly hang out "downstairs" under cover, and a couple of the hens do lay eggs in the upstairs "lodging" area. I felt sorry for the young 'possum because, well, small, immature animals have such a handicap learning how to survive. But NOT in my chicken coops/run.
It got away - moved a whole lot faster than I expected it to! - and I learned to close that coop up at night. I had been leaving the door to the bottom open because my Cayuga ducks patrol the yard all night and I thought they might need shelter. They won't use their duck house - it's been taken over by 3 chickens now.
They are egg and feed eaters, but mature ones will also kill chickens.