I believe you are mistaken. Predatory black bears usually approach with considerable caution. They are uncertain of humans as prey, so they take their time to evaluate the prey and "test" it to be sure it is not dangerous.
They close in on the person like a cat closing in on a bird. People almost always see them coming and have plenty of time to prepare for it, which very often ends with the bear being killed.
Here are cases of two geologists who were stalked by predatory black bears in Alaska. One did not have a gun and was terribly mauled, losing both arms (bears are not quick killers). The other had a gun and killed the bear as it attempted to close with her. She remembered what happened to her colleague.
Two Geologists....
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Good Stuff,Dean.