This, like parts 1 and 2, is very good. I liked learning all the new details about Simon. I do have a couple nitpicks for this one, though…
First: "Their guns he didn’t touch. Guns don’t remember far." This is a little too obscured for me. Maybe just me, but I don't get it, and I feel by this point in the story I should.
Second, and more importantly, the assassin killing self rather than talking has been done so many friggin times and this is just another run of the mill instance of it. The red scorpions are a neat detail, and so are the lines about not yielding to temptation (and calling Simon the Devil), but not good enough to save the cliche. And the story climaxes at the cliche; that's the payoff of this chapter. It's highly mediocre. We need some better payoff for the shootout.
On the other hand, this is still highly entertaining, and I was very absorbed in the story and am still eager to know what happens next, so it's very much worth an upvote.