I'm so sorry that's what happen to me a couple years ago and it was a family of raccoons. They just killed and left them laying in the run and coop. They had found a small area that I hadn't secured I didn't even realize it was a problem.
I will start collecting your eggs today for next weekends pick up.
Again I really sorry that you had to go through that.
When you get your fence rebuilt and a new batch of hens run a small horse fencer around the outside of your fence. Put the wire in 2 spots about nose height for a large dog and one the size of a meduim dog or fox. Once they get zapped only once that will give them enough deterant to leave your flock alone.
I am so sorry. I would be just devastated to lose all my girls. I hope you figure out quickly what did it (my vote would be a dog also) and are able to fix your fence and start over again.