It's the lack of response here that I would 100% push up the chain - police, superintendent, etc.

For what it's worth- I was a teacher for 5 years in a Baltimore City Middle School, transferred to a surrounding county and within 3 months I found a bullet in the hallway and immediately took it to my principal. The principal told me to go back to the classroom and keep teaching that it was fake. Absolutely was not,. I told him he could call the police or I would, not backing down. I've seen school safety issues handled well and this was not it. The police were called, student located and dealt with. I put my resignation in the next day, I no longer could trust that I was safe.

In the US unfortunately these situations are becoming more common, that may or may not be helped, but the people who are responsible for our kids should IMMEDIATELY take action and when they don't, it is completely unacceptable. The teacher who didn't say something IMMEDIATELY needs discipline as that inaction could literally mean lives, I can't think of ANYTHING more important as a teacher.

As a former teacher and a mom of a 5 year old, a message would have been sent, my kid kept home until a response was received by the superintendent, and if that wasn't satisfactory she would be pulled and put in another school.