Twenty years is a long time so we know some of you are too young to remember what happened on 9/11/2001.
It was possible for a few minutes to think that maybe the first plane was an accident but when the second hit the World Trade Center it was clearly an act of war. The third one crashed into the Pentagon and the fourth was headed for the White House or Capitol before the passengers heroically decided they would not allow that and chose their own means of death in a field near Shanksville, Pennsylvania.
What happened that day was in turns despicable and sick and then selfless, heroic and amazing.