assassination of john f. kennedy
On 22 November, 1963, John F. Kennedy, the 35th president of the United States, was assassinated while riding in a presidential motorcade through Dealey Plaza in Dallas, Texas, when he was shot by Lee Harvey Oswald, a former U.S. Marine.
As Oswald was murdered two days later by Jack Ruby (who swore revenge against him after the assassination), the event has spawned numerous conspiracy theories, ranging from the motive behind Oswald (and Ruby to an extent), that it was an outside job that Oswald has no involvement in, or that it was an inside job by those who are disapproval of JFK's sweeping civil rights reform.
Much like the later 9/11, the event (more specifically the image of moments before Kennedy was shot) has become a part of "Gen Z humor" as a dark humor punchline for shock value.