A bobcat will kill for fun. They'll also kill several things at once and partially bury them for later.

A 6' fence is not (now obvious) nearly high enough to keep birds safe. Can you close them into the barn at night so that nothing can get to them?

Sounds like a weasel,ermine or a raccoon although your description doesn't sound like a raccoon. A fox or bobcat would not go in a slaughter everything and leave it - they will pluck one at a time usually. We have lots of weasels and ermine around here and that's their profile. Fox or Bobcat would not easily go over your fence either it would take them some work.

I would put liver in your traps.

Gary:

I am so sorry for your loss. I know how you feel. I agree with nhsuzanne it was probably a weasel, ermine or a raccoon. I had the same thing happen to me went out one morning to find 12 chickens dead/missing - found 4 lying in floor of coop with heads gone-one jammed inbetween 2x4's guess could not fit chicken through the floor and 7 just gone! Was a weasel-talked to a neighbor that saw it - well it is history now! It dug through under the floor and ripped through the wall. Did however fix the coop-I won't be letting that happen again (just in case he had friends) (zone 5)

Nelda

Ever heard the phrase "like a fox in the hen house"? Now you know where it comes from. Good luck with the trap, but I've never been able to catch them. The one time I did there was a fist sized hole in the side of the wire trap covered in hair in the time it took me to walk to the house and back.

Did you happen to notice the color of this killer. When we raised chickens and other birds we always put a wire top over the pen and buried the wire a foot in the ground so coon,skunk,mink could not dig under the fence and always used the fencing with the 1/2 to 1 inch holes and no bigger, and I do know from other people that have had slaughter like you describe being done by mink, they kill just for heck of killing something, tearing the throats out and leaving the body. A bobcat or fox would eat the chicken, not just slaughter them.
A skunk will do this also. I do not know if you have Fishers in your state but they are bigger versions of a mink but kill the same way.
its heart breaking to have this happen.
Also a dog will do this and I have seen dogs climb wires fences. We shot a pitbull dingo cross that have climbed a 6 ft wire fence and was killing a neighbors chickens when they were out of town.

To raise chickens you have to protect them and to do this you have to built a pen to keep everything out.

Sorry to hear the lose