A Fisher is very fierce, and will kill multiple chickens...but they don't go completely crazy like a smaller weasel. They will usually carry one off - and leave the other 1, 2, 3 they killed just laying there. My hubby let my chooks out (at our other place) then took the dog for a 1 hour walk

- he didn't heed the 'they are only out when we are there' - because we could hear the fisher cat at night. It killed 3 of my 6 hens - one got carried off, two were left where he killed them. And I know for sure he took one, as there was a trail with sporadic clumps of feathers from her.
That was quite a while ago....fortunately, this side of town there isn't a fisher - or at least not one close to be a constant menace! Raccoons, foxes, hawks, owls and coyotes are enough, thank you!
Edit to add: Raccoons will usually kill a couple - and eat the breast and/or the entrails, leave the rest - and not touch one or more of the killed ones....but sometimes you will get a raccoon that will go wild and just kill everything, especially if they (chickens) are little (re: young) ones . I have had some raccoons that bite the head off, some that didn't. They generally go for the head/neck for the kill - unlike a fox that will usually grab them from the back and the puncture woulds will be on the sides - and they will shake them to snap their necks.