Police have a separate duty to apprehend criminals. Duh.
Sheets shot a man in the back of the head, killing him. His possible defenses are (A) self-defense; (B) defense of third parties; and © authority of law. Hernandez was fleeing, so Sheets didn’t need to be defended; no one has claimed that Hernandez was running toward or threatening another person who needed to be defended; and no one has claimed that Sheets had authority of law to execute Hernandez. So basically he seems to be falling back on the old defense of “He needed killin’.” That’s not actually a defense, either legally or canonically. And certainly not theologically.
No, you said “It’s a given fact that the thief was fleeing and shot in the back of the head.” That’s not pulling a handgun (which I guess is what Sheets wants us to believe he thought); that’s fleeing. And you’re not allowed to kill someone just because he stole your radio, or because he’s running away.
Oh, well, that’s okay, then. I’ll just shoot people whom I believe have broken the law (from behind, of course), and we’ll leave it up to my confessor. :rolleyes: