We spent some time looking at updates for the first hit on the WTC, then remembered that the Aerial Robotics Lab had a big screen TV and went down there to watch updates.
I remember warning my middle-eastern looking friends to be careful going home. As far as I know there were no incidents, certainly not among my friends.
The other similar event for me was the Challenger disaster. My recollection is that I heard about it at school because the 5th grade science teacher had one of the school's very few TVs and his class was watching it live. He cried, I heard.