I'm UK here to I had a Fox attack around 2 years ago and lost my entire flock it took my 3 smallest ones and bit the heads off the biggest 2 there was no blood just feathers everywhere I nearly didn't get anymore but I missed them so much so my husband built me a prisoner cell block H coopIn the UK here, fortunately the supplier had month old chick siblings left over which I brought over straight away but they aren't the same....scared of me and still adjusting to their new home.
I've since fortified the rear of the coop adding 2 padlocked barrel bolts to the tray slide opening and extra door bolts to any other openings, also noticed this morning new teeth and scratch marks (from the damage seen you'd say it was great white sharks biting into it!) - it tried to take it out again! Unless the fox can use a screwdriver or rip metal off with it's teeth, I don't think it will succeed.
However if the fox gets to them again, I can't go through that stress again and I'll probably give up having "backyard" chickens..


