Should his teacher have done this?

So my 16 year old brother has a project in art at school. Students had to carve through an old book and create something out of it. My brother created a hand gun out of a book. His title for it was ‘The Weapon of Knowledge’ (which I see as very clever). His teacher was all fine with it, said his idea was brilliant. He was very happy with what he created out of a book but today his teacher wasn’t there so he had a substitute teacher. And this substitute teacher told him off and said she never wants to see his creation at school again, because of the recent mass shootings in America.

A bit of background info:

-We live in Australia.

-This project was made before the recent school shooting.

I understand that people are sensitive with what happened and so they had every right to be. But I think this is way to far. And would like to know your opinion.

It was a project that happened before the recent tragedy and his actual teacher said it was all ok, but a substitute teacher told him to never have it with him again (even though it was a school project).

I am just curious to see how others feel about this.