When you talk about bear attacks you need to consider that the greatest percentage of them are just after your food, not you.
Same with Grizzly/Brown bear charges. Some are just bluffs. From what I understand in Alaska, you can't just kill a bear unless its within a certain distance and attack seems certain.
Bluff charges and bears looking for a easy meal can the majority of the time be discouraged by rocks/sticks/spray/loud noises etc.
However a small percentage of bears, usually young males are what they call " Rogue" bears.
Their very territorial and see YOU as the meal, not your food pack. They'll stalk and attack looking for a easy meal (you) :'(
If that's what's after you, you need to have the means to kill it or disorientate it enough you can make your escape. It becomes a case of you or them. I prefer it be them.

What does a " Rogue Bear" call a bald 270lb fat guy on a girls bike pedaling like the dickens?

A MEAL ON WHEELS ::) ;D