Imagine you're playing a game of tag with your friends. You run around, tag your friends, and have fun. But what if one of your friends decides to play a different game? What if they bring a toy gun and start shooting at you and your friends?
That's kind of what happened at Yale University. There was a man who was upset about something and decided to bring a gun onto campus. He didn't actually shoot anyone, but it was scary for the people there because they didn't know if he was going to hurt them.
The police came and they talked to the man and convinced him to give up the gun. Everyone was safe, but it was still a scary situation.
Sometimes, people make bad choices and it's important for the police to be there to help keep everyone safe. It's also important for all of us to remember to be kind and try to solve problems without hurting anyone.