Having botched some brain shots, I have had a chance for a second shot primarily because the ele were moving slowly after being hit with a .50 caliber rifle. Consequently immediate follow up by the PH was not required.

However, with lighter caliber rifles, the ele is often sprinting away after a head shot that misses the brain, and then the PH better shoot quick or the ele is very likely lost forever.

Another issue is whether the shot is taken at the edge of the concession and next to a national park, or 50 miles from the nearest concession boundary. The former would mandate a quick insurance shot by the PH.