You don't have to wait that long for birds to know where their new home is. They should be ready to let out by now. I've never kept new birds in more than a day or two before letting them range. They've all found their way back in at night.
WoodlandWoman is correct, chickens do sometimes kill each other, (it isn't very common) but roos don't normally kill pullets. Are you certain that pullet wasn't a cockerel? The most trouble I've ever had with chickens killing each other, is new mom hens attacking other hens' chicks, or orphan chicks being attacked by moms with new chicks.
I'd be concerned about a human aggressive roo around a small child, though. (I won't tolerate being flogged myself, either) Do you know anybody with a gentler roo, and no children, who may be willing to trade with you? Or you may just need to get a different one and rehome or eat that one. If he's pretty enough, maybe you can sell him. Just get one though, I hadn't thought about the bachelor roos suddenly having hens to fight over, factor. Your pullet probably just got chased (or was getting out of the way, or panicked) until she crashed into something and died.