Even on normal difficulty the AI will investigate when they hear you fire a gun from a distance, and every other random fight I end up in with a small two man road side pirate patrol, ends up with two or three cars worth of enforcements trying to hunt me down :). If you're lucky they'll get jumped by a tiger or a komodo dragon. If you're unlucky it will jump you will you're busy eying your ammo counter, cursing that you haven't gone boar hunting yet to upgrade to a bigger ammo pouch :p.
And I'm only three or four hours into the game having barely done anything yet aside from the first couple of story missions after the intro section.
Yea even taking a shot around the pirate will just have truck loads coming to check out the area trying to find the person who took the shot. I love this game, FPS with GOOD RPG elements in a open world.