There was someone saying their mom didn't think it could happen because she witnessed a hen sitting watching a bear eat a rooster without fussing.
It does sound like a bit of a freak event, but also not surprising given the size of the run and capability of chickens to freak out when they think...
Based on (lots of conjecture and experience with predators) the size of your coop in the picture (marketers oversell how many birds you can fit in there), I'm betting a predator (raccoon, fox) was trying to get to them and they died from fright in the run, possibly breaking their necks in the...