This is only my second year owning chickens and none have been eaten yet util 2 weeks ago. My favorite EE Light was the first to be eaten. She was flighty and escaped often. Now that same fox returned to take another. My rooster will always be remembered as a hero. The fox likely would have taken off with more if my rooster Anankos hadn't saved them. Foxes are known to keep returning. (It HAS to go.)
I am sorry your rooster did not make it. Yes, the Fox will continue to be a problem, as domestic animals are basically takeout boxed lunch for wild critters. My yard was a McD's driver thru for chicken nuggets for a while as far as wild life was concerned (years ago when I first had birds).
Do you got a dog? I found having a dog made a huge difference on preventing night raids and other dogs getting at my birds in the past. The dog must be out with the birds though to be effective.
SInce you can have roosters, try and find a replacement ASAP, you may want a breed that will attack back when threatened and defend with a better chance of survival. You for sure want a male that is dominate, that looks around a lot (as they are more likely to see threats), remember dominate in the flock or the ability to defend/attack well does not necessarily mean the bird will be human aggressive, those traits are all separate.
I have my coop on bricks (not mortared in so water can drain) to prevent midnight snacking when the raccoons, opossums and other night roamers get the munchies and prevent snakes too. The coop area is covered as well to prevent Hawks from noticing the hens. I have very small wire spacing to hopefully prevent my birds heads from being pulled through. I do let the girls out when I am around but based on my experiences in the past it took 2-3 years for the predators to suddenly realize snack packs where in my yard (I am on year 2 of having birds again so I expect soon hawks or other critters to visit). The enclosed coop (which is small) is surrounded by a metal fence (a fox could get in this bigger metal fencing but not a dog because of the type of fence it is), which is inside my fenced (combo cyclone & wood) backyard.
Some folks have security cams on their poultry area, & run hot wire around the chicken yard too.
I do have a portable fence, that I can cover too, but that is more for me to contain the girls in different sections of the yard and not what I would call a good defense against foxes.
Predators I worry about are snakes, hawks, dogs, raccoons, foxes, coyotes, opossums, skunks, weasels, cats, and mountain lions (seriously they come into suburbia here via the creek and bicycle trail system not to mention the rivers and climb over fences and take small dogs as dinner... most people never know why their poodle disappeared, but after knowing of one that was doing that in my mother's neighborhood I now know the signs of bento box lunch hunting mountain lions in this area, my kids where stalked by it when it jumped into grandmas backyard). Wildlife is abundant in my county (no hunting allowed county) and many cities within this counties borders, there is literally everything living here (including prey animals such as turkeys and deer), moving around when people are at work or asleep. I see a lot of the wildlife because my job allows me to be driving around all day through neighborhoods, I watch the sun rise and often set so I see the critters booking it for cover before the humans get up and also sneaking around after most people are at work. We got a healthy vulture population as well. The only thing I have not seen yet is bears & wolverines those critters seem to stay up the hill in the woods.
Your probably going to have to shoot the fox or trap it. Anyone in your area good at fox trapping?
Sorry