My thought, His muscle reflexes are trying to catch the gun and let go of it at the same time. The fight of loosing control and trying to gain it pulls the trigger. Yes, I've seen enough stupid things in my time that I think it's real.
Looks real to me. Definitely not full auto, there are distinct pauses between shots. The kid seemed genuinely disturbed and doesn't look like the type to go through the trouble to fake something like this (buy blanks, earplugs etc...)
Actually, it is difficult to pull the trigger that fast on a semi-auto with two hands as well, but it isn't really the number of hands that is the issue, but how quickly one can move one's finger. It is very difficult to pull it that fast and keep control of the muzzle single-handedly, but the kid isn't doing that.
My guess is that the kid isn't pulling the trigger that fast. He likely pulled it just once and the rest is bump firing.