I am so sorry for your loss. Yes it sounds like a dog attack. Back in Oct we had a dog break into our coop and kill 12 of my hens. It will be back. I say SSS. The one that got mine got away that morning and than came back that night. He will not kill anyone elses. He only broke their necks. Sounds like the roo's were protecting their hens. Once aagain I am so sorry.