He did it exactly right. He stayed behind cover, and maintained distance.
Maintaining distance is important in a rifle-vs-pistol fight. At 15 yards (my estimate from the video) a rifleman can reliably hit a thug, while a non-trained thug with a pistol is unlikely to hit him.
Oh, right. I was hoping he could close the distance and fill them full of lead. Watching them running and crawling away was heartbreaking. Thanks for the correct advice.