The message would be valid without the trauma & embarrassment...
Yeah, wow, that's ridiculous.
At first I thought, ok, they're trying to get the message across that ALL guns, toy or otherwise, are not acceptable
---- but to yank the kid out of lunch, if I read that right, & have him sign a statement in the principal's office...
Really -----
If he wasn't pointing it at other kids & threatening them
"I'm gonna kill you muthaf------" 
etc., etc...
---- that was uncalled for.
Tell the kid you as a teacher, principal, authority figure, don't like guns,

don't want to see them any size,
put it away, eat your lunch & end of story.
The fact he put it in the hands of a toy police officer too, and that his dad's a retired cop --- In context, it just gets more ludicrous.
They/the principal meant well but handled it totally wrong, a good, harmless kid should not be afraid to go to school... because of his teacher, lunch aide or principal....