To me that sounds like a dog or at least some kind of canine. I had two large dogs attack mine and lost eight. I found one body, not mangled, and two piles of feathers. There were some other feathers flying around but not in a pile. The rest just disappeared. I could also see that happening with coyote or fox, probably more than one. Maybe even a family, Mom teaching the kids to hurt.
I don't think it was a bobcat. Bobcat normally carry the remains away and try to hide them, often by burying. But I would not expect that many at a time if it were a bobcat.
I don't think it was a bird of prey. They are not going to do ten at a time. They normally don't carry them away but eat them on the spot, though they might take one back to the nest to feed chicks if it is s big bird of prey and can carry it.
It is speculation, no arguments from me on that. Just because most predators of a species act a certain way does not mean they all do. But I'm betting canine.