When I was in a very young grade at school, an announcement came over the speakers. It was something intentionally meaningless, like “just a reminder that so and so will be presenting tomorrow”.

My teacher jumped up and closed the window shutters. We were all counted and escorted to the gymnasium. Turns out that message was a coded code silver kind of thing and there were people with guns on the school grounds.

Nobody was harmed; not students nor teachers, nor gun-people, nor police. There were contingency plans in place and practiced and they worked marvellously. I look back and find it kind of neat.