I read an article (text and action photos) where a game warden had to draw his issue .357 mag. revolver when he got mixed up with a grizz. The bear was being released from a culvert trap. He emptied the six-gun into the bear at hand shake range. The bear fell dead at his feet. The warden mentioned that the loudest sound he heard was the seventh time he pulled the trigger and it went "click". I'm gessing there was a bad smell in the air too.
Robin