Devistated!

[chickens really]

Yikes!.....I feel terrible for you...My Husband put a 12" apron under the sand for my coop and we used small wire one my Coop...Not sure of the name but is strong...Yikes...I am a Woman.....lol!
I only free range if I sit with them.....Even my Ducks are protected daily....

Sorry for your loss...We all learn as we go....

 

[CluckerCottage]

We have been noticing a couple of areas around the run where a fox has been trying to get in. He left scat and it's definitely fox.
Same diameter dig holes as you describe. I am in central NY.
My husband put cinder blocks over where he was trying to get in and we have not seen anymore evidence in the past 5 days.
The chickens are locked up tight in their coop at dusk. It's built very strong and there are no gaps/holes where anything can get in.
A wise old farmer told me once that there is no such thing as a totally secure coop/run so we check everywhere every day to make sure we are doing our level best to keep our birds safe.

I am truly sorry for your losses, my heart hurts for you.