How big are the openings to your cage? Big enough for a coon to get its front paw into? I could be able to reach in. Is there blood inside of the cage? Could a raccoon have dismembered your chickens and pulled the pieces through the openings? There would be blood though. If no blood, is it possible that a snake could have gotten through the openings? Depends on the size of your chickens/quail, but a big snake can unhinge its jaws and eat things several sizes beyond the size of their heads.
I found a 5 foot black snake in my coop, several times. I finally caught it (the third time!) and put it in a bag, drove 20 miles away and let in go in an uninhabited section of woods around where we are. Caught a second snake the same day, right after I got back from taking the first away, it was right along side of our coop where the nest boxes are. I put that one in a bag and took it away and let it go too. We think that the snakes were entering our coop during the day when the door was open and was eating some of our eggs.