With that much loss, it's probably multiple predators and possibly multiple species of predators. When predators hear the chicken distress call, they come running hoping for an easy meal. All the predators in your area may be joining in the feast.

Keith

"Weasel in the Henhouse!"

Well I set a conibear in the entrance to the coop with a wire cage behind it, so no chickens could get out. No catch and no chicken lost. Found no track in the mud.

Had a coon over the weekend get 30 out of 33....3/4 grown bantams...everyone heads off....5 or 6 head gone and crops eat out...

How did you know it was a coon?

Game cam...he fell to bacon grease and feathers next night

I've never had a racoon kill more than one or two. But based on the responses in this thread, it must happen.

Mine started in the roost...and finished the rest out in the run...almost like it was a sport...

Never forget that a Norway rat can and will kill with the same M.O. as a mink or weasel and they can kill the largest of breeds !

Many will try to trap a mink, which is actually a rat

Yes. Only the heads were gone from all of them.

To get whatever it is with non target animals around you have to exclude the non targets first. You can make multiple narrow chutes with boards or fencing so only the offenders can get in and set those heavy with traps. I agree with Lt.Grey . My first suspect when chickens are killed in a chicken house is definitely rats--but they don't usually roam around outside and kill them there, so they're not likely the culprit this time. But as I found out--don't underestimate a rat. And don't think rats are all easy to catch.

I had one of 5 chickens killed inside the chicken house with its head missing. The only access was one 10 x 12 inch entrance door at ground level. In front of the door was 8 inches of fresh snow. There were no tracks in the snow, only light scrapes on the surface. The killer turned out to be an owl. Also doesn't seem likely that an owl would be your culprit with that amount of carnage, but they definitely eat the heads off chickens.
If you have to, move the chickens temporarily, get them in a SECURE structure with limited access and festoon those access routes with traps.

I knew an old trapper here that used to only use chicken heads on his mink sets.

What ain't you got one of them there AR rifles. Heck way guys talk on here it will defend everything you got against everything there is......