I live in the Yukon, and I can confirm that when confronted with even a medium sized brown bear the last thing the world you'd want to do is shoot it with a 9mm sidearm.
While I wouldn't shoot one with a 9mm, just a warning shot is generally enough to get a bear to move on unless you've already deeply pissed it off some how.
When you're dealing with a bear that has never seen people before, it has no idea that loud noises like rifles are dangerous. I've seen a friend fire a .375 right past a brown's head from 50 yards and it didn't even blink. The bear just kept eating berries sitting on his butt.
You can lay on your horn in the car, fire bear bangers and smash pots and pans together - they don't care.
I've also seen someone unload into one with 5 shots from a .303 - all shots hit home in the heart/lung area (later we found both lungs torn apart, though not the heart) and it kept running full speed for over 100 yards. If we had been closer than 100 yards, it would have had us.
