Mass arrest

Okay kiddo, sometimes when lots of people are doing something illegal or dangerous, the police might need to arrest them all together. This is called a mass arrest. Imagine you and your friends are playing a game, but one friend starts to cheat and break the rules. The teacher tells everyone to stop and because your friend won't admit to cheating and won't stop, the teacher decides to punish all of you. It's not fair, but sometimes it's the only way to stop the problem. That's kind of what a mass arrest is like: it's not fair to those who didn't do anything wrong, but it's necessary to stop the bad behavior.