I was in school at the time. The teacher had it on the tv when I walked in (just after the first plane hit) and I was so excited to watch an action movie instead of doing work. When the camera didn’t change the view for a couple minutes, everyone gave me the stinkeye when I criticized it for being boring.
Then my teacher explained what was happening and told us all to rmember it because people will ask us for the rest of our lives where we were when this happened. I didn’t get it at the time, but he was right.