Sounds like a malfunction that almost ended in a run-a-way gun...luckily there was a failure to feed.
Unless he intentionally modified the AR15 to shoot multiple rounds per trigger squeeze...he's not guilty of anything.
Whoever the jurors were, they are freakin' morons.
The 1st and 2nd Amendments:
The pen IS mightier than the sword; but when you run out of ink, I will be ready with plenty of ammo.