Usually there are quite a few "Hey bear"'s before you resort to blowing its brains out.

making your presence well known ahead of time by being noisy can help, but it doesnt always, and thats when you can have a 3/4 ton animal suddenly bolting at you from thick bush in about 2 seconds, because its decided to lay in ambush to kill or wound you rather than give ground.

and really the moose are a lot more likely than bears to go after you.

more qualifiers as well such as with calf or cubs, hunting and predation engagement being interrupted ect.