I am so sorry to hear that. That is a tragic thing to come home too! We too had a dog get in our yard last year.
We live with a park/green belt right behind us. We were cleaning up rocks out of the front beds, and taking them by wagon to the creek behind us, so our back gate was open. A lady was walking her dog, and let him off the leash, and of course he got in our yard and tore through the chicken wire and got my Golden Lace Dotte and a few other chickens.
I was so mad, and the owner didn't think it was a big deal, because we left our gate open. HELLO there are LEASH LAWS!!!!!
This new chicken coop will have plywood surrounding around the bottom, and a hot wire running around the bottom to help discourage that from happening again.