In my younger days we, of course, had to set up a target at a construction site and try this ourselves. The thing about those 22 cartridge nail guns, is they are made to fire a nail at high speed into concrete or some other hard material. They are NOT made for range; we literally couldn’t hit a target ten feet away most of the time. The nail is not aerodynamic in the least and tends to lose momentum and just go into spin as soon as it leaves the gun. So, unless this guy was literally just running up to people and shooting nails directly into them (which I guess is possible) I find this rather implausible.
Thanks.