I was in college when the towers fell. It was my second year, so luckily I already knew a bunch of people at RIT. I got out of class and immediately one of them told me (in person) that a plane hit a tower. We still thought it was an accident.
The worst part was the uncertainty. Huddled around a TV with other friends in the dorms, just no idea what's happening. Seeing a tower disintegrate on live TV, having no idea what we're seeing.