Folks here should spend some time reading the "New Members Intro " thread to see how very common it is for their new chicks, flocks, whatever to be wiped out in minutes.
The usual scenario is it's the owners dog (cats too) that massacred them. I have been a dog lover all my life but I still believe Dogs and chickens should NEVER meet. A chicken has never killed a dog (or cat) while dog & chicken encounters frequently end in death for the chicken. The dog has fun, the chicken does not..
I was surprised by the number of times the predator was a small or toy breed of dog, frequently a Chihuahua, Yorkie, Doxie. I wouldn't think them capable. Certainly other breeds of dog (and mutts) kill plenty and it is easier for them to muscle their way into a coop or pen with poor or no locking device. The small breeds can slip through more places, dig under, or just wait for their chance to be free when no one is watching.
X2. Too many things like chicken. I used to free range not anymore.