First off, welcome to this site, it's a good one. It may be wrong but on that last bear, I'd have put a round into him. It may kill him, it may not, but it sure would discourage him. He's acting aggresive and approaching you, I'd have shot him. I think I could make a good case for self defense. My first thought though is why would he have given his rifle away to his partners to carry down for him and allow himself to be left with only a .45 ACP when he's already seen 2 previous bears? I'd also notify park rangers of aggresive bears in this area.