I am so sorry for your loss. I know how horrible it feels to find the remains of a chicken who was attacked by a predator. It was probably a raccoon. I have tried to make my chicken run a fortress after my losses. We put metal siding 3 feet high and dug it into the ground to help prevent digging and climbing. The upper part of the fencing is welded wire, and we even decided to cover the top with welded wire,just in case a raccoon does find a way to climb up the side and to keep out raptors.