In the sense that he had a good reason to shoot, yes. Because it looked like the guy was reaching (because he was trying to pull up his pants). Hell, the edgyboi 'psychopath' even gave him a second chance after he did something strange which would have justified shooting earlier.

Nothing in this should justify the quite bad way that they went about doing this - it makes little sense to have the guy crawl towards you rather than tell him to lie on the ground with his hands on his back.