The fact is, black bears are not primary predators. They will usually retreat if they hear you coming. They are mostly scavengers and vegetarians. Much different than being in grizzly country.
This was not a short and spontanteous attack, it was prolonged and involved different 'acts' of attack. First the little boy, the mother fought it off, along with other adults, but the mother was drug down the trail, and then, the girl, apparently got seperated from everyone else, and was attacked in another location.
I'm wondering what the incidence of rabies is in this area and whether it's possible that's what's going on here???
In the end, if you're going to be in the wild you should be prepared for the unexpected, i.e. Have two full clips of nothing less than a 9mm on hand.
Update: A bear (possibly THE bear) was caught and killed. No rabies. Awaiting the necropsy for stomach contents. Paws seem to match prints at the attack site.