Yikes. Amateur hour.
As I recall the kid had an adult standing by him when the incident occured. He should have had someone helping to hold the gun and there should only have been about 5 rounds in the gun.
What's worse is that the 15 year-old repeatedly told the father of the kid that the Uzi was probably too powerful, and that he should choose something else. But no, the father insisted he get to fire the Uzi. However amateur, the teenager actually had more sense for the kid's preservation than dad did.