I've had that happen to our chickens. 2 different neighbor's dogs have killed our chickens (4 of them in total - that or scared them off to the point that they didn't come back - they were free-ranging - but it's nothing compared to your 29 - :( ). Now, we have had to build a much larger...
My little Bantam rooster seeking refuge & sleep on my Buff Orpington rooster. You wouldn't think that 2 roosters would be happy with each other, but they loved each other (until this Buff got killed by a neighbor's dog). :(