There are several astonishing aspects to this tragic incident:
What were they thinking?
That's the point of course - they weren't thinking, else they would not have been there at all. The parents and the instructor are wholly to blame. As a consequence, the instructor lost his life and that little girl will live with the memory for ever.
Sadly the NRA will continue its powerful lobbying and prevent US law being changed to protect the nation's children; we will inevitably see this happen again.
"Those who live by the sword, die by the sword."
Think about that, America.