Refrigerate until the rigor has passed. Can take a few days. You can tell when the leg moves freely. I usually put mine in a plastic shopping bag and tie it shut, then refrigerate for 3 to 5 days. Then I freeze it or cook it. Not sure if one day will be long enough. If he is still in rigor when you cook he will be pretty tough.
The other way I do older birds is a pressure cooker. If you cut them up and have a large cooker you can do two at a time. 20 minutes at 20 pounds. Then remove the meat, strain the broth into a cooking pot and a low boil until it is reduced to about half. Then I measure out the meat in 2-cup lots and freeze the meat and stock separately to use in casseroles and soups. Course you can use some of the meat fresh for a lovely chicken salad. I let the chickens pick the carcass clean and they get the skin and neck, too. I boil up the liver, heart and gizzard separate from the rest of the bird for dog treats.