You really think you could kill a charging bear with a pistol? First you have to hit something running super fast, then you gotta hit it in the kill zone, then you probably gotta hit it again. You also have to be loaded and aiming during the attack-ie you saw it coming, which may not be a possiblity at night.
I've dropped a brown bear in Alaska with using a 44 magnum with a 2.5" barrel. One shot of buffalo bore 300grain. I then had to hike 14 miles back to the ranger station to report it. That was during the day, and I did see him coming. I hit the first time. I can't say that it would be the same if I needed to do it again, especially in low light. I did however spend a few quality years learning to shoot at night.