Pretty sure this was one or more dogs playing with the hens, aka killing for sport.I would think weasle they kill for sport.
I've had a weasel. They kill to blood the hen, drink the blood then kill another one. They never take out the whole coop unless you are down to under 3 birds, 2 or 3 good sized birds a night, or 5 pullets.
One weasel- took out 14 australorp pullets and I think 5 adult birds over a period of a couple of weeks at my place in 2012. I learned to weasel proof the coop, left my dogs outdoors surrounding it at night for a month and the deaths stopped.