Oh i see.A properly trained dog ie protection etc should always growl/bark 1st stage first to let you know it's not happy or under threat, then if the situation changes ie
the dog becomes more threatened then the 2nd stage is the attack.
So lets get this straight.
One bark - be scared.
bark and a growl - shoite yerself.
Brilliant, i feel reassured already.
Stupid kid must have missed the growl bit
Nothing to do with the kid being stupid.
You state the dog was well trained. Somethings wrong, so it wasn't well trained in every aspect.