Perhaps the bear was used to humans, either feeding him, or bothering him. But I can understand the runners, too, it's hard looking strong and aggressive when you're just in skimpy shorts and soft shoes. All bears that I have encountered when running either did not notice me (and just passed by), or they turned and ran away. I am not sure if I'd have the guts to stand my ground and yell at the bear if it charged toward me. Depends on the distance, I guess, and I try to be smart and keep some space between me and the bear, even when I'm watching them. Fortunately it's not that often that you literally run into a bear by surprise (if you stay aware of your surroundings).