QUESTION , why does instructor zero keep shooting the ground in this hostage drill ? (video link inside)

this is the drill https://youtu.be/ZqGVU1sW8pg?t=47s while he says "stay back stay back" he shoots a few rounds into the ground off to the side, i know nothing about pistol fighting, i am just curious via /r/CCW http://ift.tt/2v9Tz4W