! Really sorry to hear about the dog getting your chickens. I'm of the opinion that a dog is the most dangerous predator to chickens because, with wild critters you know what you are getting. Dogs...one minute they can be your friend, the next....
Hope you can chickens another go - good luck.
Sorry for the circumstances. Report the attack to animal control so that you are on record about having a problem with this dog. I you know who owns the dog, inform them of what happened and that it will not be tolerated a second time. Again, so very sorry that you hav to deal with this.
Welcome to the BYC site. So sorry to hear about your chickens.
I agree that dogs pose perhaps the biggest problem for chickens. They are not afraid of human scent, like to chase anything that moves, will kill for fun rather than for food.
If you know whose dog did this, you may get some financial restitution. Not that that helps with the loss of a feathered friend.
If you don't know, then plan to build dog-proof coop and run areas before you get more chicks.