If you are good enough to quickly put a bullet in the shooter’s face, you are good enough to put one in the shoulder ball joint thereby preventing the shooter from making followups yet remaining alive to tell his story.
You have no idea how much of the shooter the snipers could see from their position. The shooters building has a slight slope, and his body appears to be on the back side. You can see the slight slope on video showing the body up there. If you look at the google earth overhead you can then see how the building is oriented with respect to where Trump, and the sniper team was positioned. Its fairly possible that the sniper team only had a head and shoulder view of the shooter, since it appears they did not see him until after shots were fired, but it appears they were looking at something in the direction of the shooter, possibly looking for what the bbc interviewed guy was pointing at. Again, active shooter, you shoot to kill, not to wound.
I would have shot the tip of his right finger off so he couldn’t pull a trigger.