I am so very sorry to hear this
I grew up on a small farm and we always had chickens and we had a big ole st. bernard dog whom I loved very much, he was my baby! Anyhow, he killed some of our chickens and ducks and I loved them too...I would hand feed them everyday--they were so tame. It is heart breaking to say the least. When my dog went on his killing spree, an old farmer friend of the family's told us to beat the dogs butt with the bird--don't hurt him, but get his attention and then take one of the dead birds and tie it onto the dogs collar and let it rot off. We did this and he never touched a chicken, duck, goose or turkey again...EVER. Someone else in the post suggested this as well.
As an adult, I had my own little farm, bunches of chickens, ducks, geese and a couple turkeys. I had three dogs that were kept in a nice large fenced in area with a plush dog house and the fence had a hot wire strung around the top and we took tent stakes to hold the bottom of the fence down so they couldn't dig under and push the fence up. I knew my dogs couldn't be trusted around the chickens, they weren't raised as babies with them...we got the chickens later. When we built our chicken coop, we had redwood 4 X 4's all around the bottom of the chicken yard wire that it was all nailed to and it was 6 feet high so nothing could get inside from above or below. We had our property all fenced so in the summer we let our chickens, ducks and geese out of their yard to roam the property during the day, but we had to make sure the dogs weren't out of their yard.
I know you're really angry with your dog, I know I was. My dog didn't know he had done anything wrong until he did it once and got beat with a dead duck and wore it around like a necklace until it rotted off. He knew then. I hope you will give your dog another chance, I know this is tough, but it is a learning lesson for you and your dog...and it only needs to happen ONCE. Everyone deserves another chance. I'm sure your dog loves you unconditionally and I'm sure you don't really want to put a bullet in his head. Again....I'm very sorry to hear about your loss...it took me back to when I was a kid and my dog, whom I loved so much, did the same thing. And thanks for posting the pictures, I agree that though they are graphic, people who have never had chickens before and are going to bring them home to share a home and yard with their family dog/s....need to know that this can and will happen with some dogs, if precautions aren't taken.