Sorry to hear that, Katy. Ive been there, an entire flock wiped out by my own beloved dogs.
You have to now teach the dog to avoid his instincts and leave the chickens alone - no easy task. Rat terriers are some of the worst and they now have had their fun. My mom had them and Ive seen them go crazy on chickens.
You have to shore up the defenses, too, with stronger fencing and self closing entry doors. NO chinks can be allowed for the dogs to get in or the birds out. You may need to resort to electric wires around the chicken pens
Some dogs are better than others, but if you intend to keep them, you have a challenge. Once chicken killing gets started, you are in for it, Im afraid.