Don't know what a DA would think or what a jury would vote, but it is not clear at all to me. What I think probably doesn't matter, because at my age and state of BPH, I am probably not going to be a juror, but many scenarios strongly suggest that a finishing shot on an allegedly incapacitated felon may be a reasonable response.

When a burglar is legally shot and finds the floor, does the homeowner always know that he is the only potential assailant? Should he turn his back on him? A prudent homeowner would kill the first assailant before attending to his accomplices, if, in fact, that is what he reasonably intends to do next. Whatever the reason for turning his back on a burglar, if the turning is reasonable, killing him is ordinarily reasonable. While I will probably not be a juror, I would hope that other potential jurors would see it the same way.

Lawyers' opinions to the contrary don't count. That's how the law works in the US of A, at least until jury trials go away.