Lots of people with guns

First of all, I’m playing on nightmare difficulty, which is probably why this is the case, but why are there so many people with guns around the place? I swear I look one way and there’s a group of people with guns, then I run away and bam, more people with guns. I can’t go anywhere without people with guns shooting at me. Also I want to say this isn’t me just crying/whining about this, it’s nightmare difficulty and it’s just something I want to ask about lol.