If Childress was headshot (and from the video it looks like the last shot was, by the way he went down), a team of Boston surgeons probably couldn't have helped him, much less the average LEO.
Not being willing to shoot an unarmed man is a foolish thought... How do you know he's unarmed unless he is naked? You take a big risk engaging in any kind of fight besides a gunfight while carrying a pistol. If it is taken then it can be turned on you or any number of innocent bystanders. Not really a smart risk to take.
Get your high school ideas of being a tough guy out of your head or take off the damn gun.
'Merica: Back to back World War Champs