Absolutely nothing wrong with children experiencing and participating in the sport of shooting. The mistake lies with the instructor, (who I believe was an army veteran and should have known his stuff)
As a firearms instructor many years ago, it's my opinion he was stood in the wrong place, he should have behind her, to the right (the recoil was bound to allow the gun to sway to the left). Even on fully auto, he shouldn't have had more than a few rounds in the mag.
A fatal mistake and a very sad outcome, im afraid.
Some people just don't understand, and the very saying 'guns don't kill people, it's the people that do' is very, very true.
The whole outrage of kids shouldn't use guns is just crazy, taught well and educated correctly there isn't a problem. A quick google search finds plenty of sad stories about children hurt or killed on karts or motorised vehicles, that doesn't bring the same amount of outrage...