I am so sorry to read your post. How dreadful. I think the first thing I would do is look for any holes or entries into their coop and get them fixed up quickly. Whatever did this will come back again and you certainly don’t need this. If any of my hens or roosters die I plant a tree over their bodies. Anything really so that I have something positive to gain from it all, and remember, if the hen was a special friend to you.
I would also suggest getting a trap. I have one which simply cages the perpetrator whether it be dog or whatever. If it is a local animal you can at least have the satisfaction of making sure they are monitored by their owners in the future. If it something wild . Drive it miles away to a place where it can catch other forest animals which are not caged.
I am sorry for your loss.