Hey guys, I'm trying for the $5000 bounty achievement and I'm having a little trouble. I know the building trick, I'm basically just camping out on top of the gray building in Blackwater, but every time I've killed most of the people, no one else is respawning and there are a couple of lawmen under my balcony perch. How can I spawn more people without getting shot by the guys camping under me?

Here is what worked for me:
Shoot a couple of people until the law gathers under the balcony. Hide until the wanted status is gone, afterwards some new civilians appear that can be shot. Took me about 45 minutes to get to the needed 5000$ bounty.

Just shoot some marshalls in the desert and then just do it again and again untill you hit 5 000. Just be sure to bring medicine!

Make sure it's daytime when you try this achievement.  It makes it a WHOLE lot easier because it's more likely people will spawn.

When you got some decent guns, just run between Armadillo and MacFarlane's, that's how I got it in no time flat.
 
Shot them poor sods of their horse the moment they came into view.