Many have found that the "quick follow up shot" is not the best thing to be thinking about after big game has been hit with a shot.
If the shot was well made, just standing there quietly and listening to determine where the critter went (assuming they weren't dropped on the spot) is a wiser thing to do.
After a bit, reloading the gun quietly and carefully gives time for the shot to take effect.
While all of this waiting and slowly reloading is going on, the deer, not expecting to be shot was suddenly startled by the sound of the shot and the impact on its body.
It naturally will try to run away but it often will stop fairly quickly to see if anything is following it.
Since the hunter (in this case) isn't following, the deer will often begin to feel the effects of the shot so it will lay down for a minute.
In most cases, that minute will be its last.
IMO, the worst thing a hunter can do is to rush his reloading and go stomping off into the woods as fast as he can.
If the deer hears any of this activity, it will keep going as long as its feet can carry it.
Just my opinion and worth every cent it cost you. :grin: