Like millions of others, this is how I found out:
It was the end of the innocence for me.
Chills watching that.
I've waited a day before reading this thread, having already weighed in on Facebook among people I know IRL, and clearly among more age peers where my having heard "Meet the Beatles" when it came out in the winter of my 5th grade year is no big deal. It was a household purchase, not really my older sister's, but something my mom bought and said I had equal right to listen to.
It was just a few months after the JFK assassination, which was a world-changer. Yesterday I grouped Lennon's death with JFK and 9/11 as my Top 3 "Where were you when...?" remembrances.
On December 8,1980, I was at the Brooklyn apartment of a co-worker. I worked for a (mostly jazz) record company. It was a non-company holiday gathering. Most everybody there was a serious music fan. The news took the air out of everybody, as much as it seemed impossible to grasp or believe. I went back home in a saddened daze.
The record company was on West 55th St, so I got myself up to The Dakota the next day or so, just to be among other people. By that time, I had thousands of records, my musical tastes had exploded in so many directions, and the Beatles members as solo acts held little active interest for me, though "Double Fantasy's" recent release held some hopeful signs after a hiatus during which John was otherwise thought to be depressed and hiding out in The Dakota smoking pot & watching TV.
John remained my clear favorite, mostly because of "Plastic Ono Band" and "Imagine," and politics that resonated with me (See "Working Class Hero"). I'd claim that he retained the greatest artistic integrity.
I still liked the full Beatles catalog, I still do. It's great. Full stop.
I got to experience The Beatles in real time, with their records as new releases, including "Let it Be" (also as a movie, in theaters) during my junior year of high school, the year I first began to listen to music with a voracious appetite that has never dimmed in a half century (holy cr*p).
Somebody asked for recollections, so I hope that wasn't too much.
Oh yeah,
@Deepster posted about his daughter at 5 taking note and asking, "Who's that?" when she heard their music. My daughter did the same thing at 4. When I told her, she asked, "Why are they Beatles?" I don't know what that meant, and I don't know how I answered, but I've never forgotten the question.