What a truly difficult time. There is just nothing like losing your birds. Hang in there, keep a small group and watch them closely. These days will pass.
If it is a mammal doing the killing, then place cyanne pepper around and under the coop, but be aware of your own critters as this is going to make them sniff, sneeze and eyes water. Also Strong smell/powder like baby powder will just drive some of these critters away, just don't let your babies near it (chickens or dog, the cat will go around it).
Good luck to you, hang in there and remember that we are all thinking of you!
Kel