Yup, definitely a murderer. As others stated, as soon as he was no longer in danger the self-defense as a defense goes out the window. I would have knelt down, pretending to give him mouth to mouth and then sucked his soul out of him.
OMG wouldn't soul sucking count as marriage?
This goes down as a case of excessive use of deadly force. He should be tried on murder charges for cross that line. Now some people in the media are overlooking the fact that the kid came in to rob the store in the first place, and this is being made into a race issue.