Sorry for your loss. I lost 7 to foxes over the past 2 years. If they see an opportunity they take it. One waited until the pond froze ( I couldn't get them off) and she nabbed 2. In the spring the duck pen door was open a smidge at the very top. She forced her way in and took the other 2. We got rid of her and her 6 pups. New fox will always move into the area once the old one is gone. The new fox got 3 this summer. I had my new babies in a pen outside. There was a 1" gap on one side of the pen. Fox grabbed the baby's legs and chewed them off

( my Indian runner lost a leg as well. Indian runner couldnt function with out a leg and eventually died. My Chinese goose tried to fight the fox and lost

( The fox comes to the pen every other day to check. I bought a medium havahart trap which was too small, get a large trap if you want one.
I think the best course of action is a large havahart trap, bait, and a gun.
My ducks/geese have a large pond they hide out on all day but I have to pen them at night.