^ This guy.
(Well, probably an ISTJ 1, not an ESTJ 1. But I know for sure that I'd be like that if my moral code warped itself around and I decided to start killing people.)
Edit: Either way, I'd kill for moral reasons that I truly 100% believed. I likely would have a small element of ritual in there, just to show that there was "karmic payback" as I perceived it in the person's death. (Not for my own personal glory, because I'd perceive the whole endeavor as For The Greater Good.)
Another edit: I'm going off of the "killer" vs. "serial killer" distinction that Marm made. I recognize that you couldn't call Rorschach a serial killer.