unti they aren't. I know that owners of pits love them, see them as sweet and gentle dogs. They wouldn't hurt a fly. But the problem is that even though some of them can go their entire life without the switch getting flipped, if it does flip the results can be fatal. Pit Bulls are dangerous dogs, as are some of the other bully breeds (like the Presas, mentioned in the article). Even though other breeds may bite or even attack just as frequently the issue is that the Pits and similar fighting breeds have the strength and tenacity to ensure their attack is as effective as possible.
It is unfortunate that this caretaker lost her life. I assume that the visiting Presa disrupted the balance of the "pack" and she stepped in to break up a fight or the visitor went after her and the pack mentality took over with the others. Who knows but the bottom line is that she got too comfortable with a dangerous type of dog and paid with her life.