Sorry for your loss. It is a risk to let the chickens out. I have bantams I let out during the day most days. I know I could come home and find them gone. My dogs had a hard time leaving the chicks alone before they clucked instead of peeped. They just want to play with the chickens and don't realize playing is harmful to the chickens. In my case, it happened in a flash.
I wouldn't be too hard on your hubby. Stuff happens. It is sad but it happens. There are neighbors dogs, cats, hawks, foxes. raccoons.....All sorts of hungry beasties to worry about.
Sorry about your loss - I know it is heartbreaking,
Caroline