You can refrigerate the carcass but the fresher it is the better the results. I've had a bird that I felt was beyond my help euthanized by T he same people who did the necropsy..sometimes they will do that for you. It's too bad but unfortunately it does happen occasionally to all of us. Sorry you are having to go through this. Sometimes though there can be nice surprises so just do your best to keep him comfortable..he might improve.