I know exactly where I was when I heard about Challenger blowing up - I can tell you exactly which desk in which room, the color of the walls, what I was supposed to be doing but wasn't... (I learned how to french braid my hair in study hall that year.)
I remember watching the replays on television over and over and over before lunch and then we were supposed to go on with our academic day.
Listening to the NPR coverage of it being 25 years (how did I get to be so old?!) there was a reference to the shuttle explosion later on. That's vivid, but for different reasons- I was trapped in a traffic jam, desperate to get home, and turned on the radio for a distraction. Certainly a distraction...
My heart breaks for the families of these brave men and women, and I do not say that lightly. RIP.