Put the body in a plastic bag.
Put the bag with the body in it in the refrigerator.
Take both to a qualified reptile vet and ask them to perform a necropsy.
That is the only way you are going to know what happened.
Now brace yourself for the probable onslaught of armchair vets who will give you their $0.02...which will be incidentally worth less that $0.02.
Vet. Necropsy. Only way you are going to know what happened.