I don't know that anybody would have necessarily been charged and killed. I am not so sure that wild dogs in a zoo enclosure behave all that differently from packs of roaming dogs, wild or domestic but loose, that one encounters in the countryside.
Dog packs are known to go after people, but they normally go after children or the elderly. Healthy adult humans can often scatter them, at least for long enough to get to a house or a vehicle.
As far as the wall, accounts vary. Some say 14'; I read 11' in the newspaper, plus a safety net on the way down.
All I know is that I'd like to think most of us would at least try to do something, in such a situation.