Some things that I don't like about 30 Days of Night

[That_ghoul_ava]

We're probably putting more thought into this than the director did.

Three reasons I can think of for being quick on the draw:

1) Her fumbling around for the gun probably wouldn't have been as cool, and it needs to be quick to have the element of surprise - you weren't expecting her to pull a gun.
2) If she fumbled around, those damn feminists would scream the director was implying women can't handle firearms.
3) Wouldn't you make sure you could handle a gun if you had to pull it on a large, horny oil worker? He won't politely wait.

The only reason I can think of for why the other vampires didn't jump in is an animal or tribal mentality - it was a direct challenge to the Alpha, a fight for dominance. Or they just didn't expect him to win.

As far as waiting for the sun to come up, I think he expressed the need to stop them - otherwise they would just move on and do all this again. The town was about to blow up, and without the survivors (and there wouldn't have been any had he not done that, most likely) the deaths would have been chalked up to an industrial accident....which is probably the better option, when you're the only person alive in a town full of slaughtered people and try to blame it on vampires to investigators.