Actually Whitman was less than 20 months. Yes, Oswald was much much longer, and even longer yet since he qualified as sharpshooter (barely).
No, it wasn't "much much longer". Oswald qualified as sharpshooter in Dec 1956 and discharged Sept 1959. Whitman qualified as sharpshooter between 1959-1960 with a score just three points higher than Oswald. Whitman was discharged Dec 1964 but during that time spent 30 days confinement and 90 hard labour. Do the math, to any reasonable person that's not "much much longer".
Disagree
So? Am I meant to be bothered?
Who could know for sure except Oswald? As a result, the question you asked necessitates speculation. Simply because we can't enter his mind to answer that question with certainty doesn't eliminate the evidence or create doubt of his guilt as you erroneously imply. But if you want speculation, Tippit is armed. If Oswald is not absolutely certain that he is dead or incapacitated, he still poses a potential danger. So Oswald finished him off. Better than getting shot in the back as he walks away.
