I think its commendable for the principal to handle it internally.
People are way to sue happy in this world. The staff member is an idiot, he isn't a criminal or a terrorist. How about he gets reprimanded and whatever internal policies they have are used and that's the end of it.
No kid was injured, killed or permanenly scarred for life. The staff member is stupid, that's about it. How would this have been handled 50 years ago, before today when everybody needs some sort of pound of flesh from everybody else and needs to make lawyers rich?
It was stupid, but you figure the person was probably a youngster not even 21 yet, and his or her whole life could be ruined over this, esp. if s/he goes to jail. "Hate the sin, not the sinner"?