I know where I was for that one too — watching Monday Night Football with my dad. Howard Cosell broke the news.
I was ten years old at the time. I remember the evening rerun of “Welcome Back, Kotter” (that was on at about 7:00pm in my locale) got preempted by news coverage the day after the shooting when countless numbers of people were outside the Dakota building gathered to mourn the horrible and senseless event.