You could very well be right; he HAD to get the money, and the sheriff had double-crossed him. And good catch; he didn't flinch when killing. However, neither did Veronica, though she sure had good reason.
And why did Eric try and save Veronica? He could have been doing the right thing, or, he could have been wanting a diversion so he had a chance to swipe the money. We just don't know. That's one of the problems with 1st person narrations; you can't definitively state any character (other than the protagonists' ) motives.
And yes, Eric does have his bad sides; annoying kid bothers are a fixture of gay fiction, after all.
Me thinks thou doth protest to much!
Who? Me?
........I think Cj has "Future" plans for Eric, seeing the reaction he received from his readers, Oh yes I see it in the eyes above me that what I predict is true. Course he will need that evil sidekick Shadowgod!