Unfortunately without camera footage (and being unable to see into the mind of an animal) we'll never really know what happened. Possibly the hen could've had a heart attack and simply died, and somehow her sudden death caused the other 2 to stress out and then flip out on the pullet, but who can say for sure?I almost wonder if the disruption was so much that my existing hen was attacked or too stressed leading to her death. Of the three she was the outlier, with my tiny alpha pearl and her big sidekick Molly being a pair. They were all hatchmates but merida rip tended to kind of hang on her own a bit more. I did find a new flock for the baby, so I'll just hang with thing one and thing two until they go to their reward. They both wanted me to love on them today, but they are stalking that babies pen like velociraptors. Pacing pacing pacing and trying to force their heads into the wire. They want to kill her too. They have also gone after the dogs and cornered the corgi.
Is this a Red sex link thing? Or do I just have really mean hens?
RSLs (assuming they're RIR based) can possibly be more aggressive, but still unusual for chickens to suddenly turn on a bird they've already been socializing with for a few weeks, especially if the pullet wasn't showing sign of illness or anything like that. If you'd simply thrown the pullet into the coop without any introduction, then maybe, but from all indications a proper introduction was done here.