With bodies strewn around, I want to say dog... How much were eaten or were they just dead with blood? I wonder if dog made a kill and something like possum came by and started to dine.
Years back, I lost my whole flock of 20 some birds to a family of coons in two nights. The first night they went under the coop and took half the birds out killed them and dragged them away. After that fix they learned how to open the door and killed everyone. Thing with coons here is though, is that they took all the bodies and I didn't find any more than a few wings and a the comb of my big roo.
Needless to say that weekend, I got a have a heart and set it becides their prevoius point of entry, caught 3 coons in 3 nights and didn't have a problem for the rest of that year.