How old and what breed is your dog? Under what conditions/what was the scenario when your dog killed the pullet? (On that note, how old was the pullet?)
My dogs protect my chickens by guarding against potential chicken-killing varmits, and killing any predators that dare test their defenses. My dogs are the main reason my free-range flocks remain safe and alive in my rural, heavily wooded area. But i put a lot of time into closely supervising and monitoring them around the chickens for many months, until i am sure they totally ignore/are completely unreactive to a chicken's presence and antics. Until then, when im not around the "dog in training" is penned separately from the chickens, with no ability to interact with chickens other than observing them through the dog's 10x10×6 dog kennel run.
Dogs can be a chicken's best friend/protector or their worst enemy. There isnt much ground in between. The difference usually depends on a dog's breed (prey drive), age, & perhaps most importantly of all, a dog's willingness to please. From a dog's view, chasing a squawking flapping chicken "toy" is great fun. Is your dog willing enough to please you to give up its innate desire to chase a chicken? The fact your dog has already killed will make (re)training much more difficult. I agree with the others its probably best to keep your dogs and chicken(s) completely separated from now on.
But IF your dog was unsupervised when the killing took place, IF your dog had no idea or understanding that killing chickens is completely off limits, and IF your dog is very willing to please you and ignore its innate instincts, with patience & time you may be able to teach it to coexist with chickens.
