The assassination of President John F. Kennedy on Friday, November 22, 1963, changed the US forever.
No one who watched the events unfold that weekend could have known how profound the change would be to the nation and its people, but we did know that what we saw on television was unlike anything we'd ever seen before.
The US is marking the 50th anniversary of the assassination in various ways - new books, special issues of magazines such as Time and Life, and new considerations of the singular moment in history in other media.
But it is particularly significant that the event will be memorialised in documentaries, re-enactments and news specials on television - not only because baby boomers remember spending that weekend watching the aftermath of the assassination, but because the abbreviated Kennedy presidency represented the emergence of a new and dominant role for television in news and public discourse.
Just as President Barack Obama mastered the use of social media in our own century, Kennedy understood that television had grown beyond Father Knows Best and The Original Amateur Hour.
In the mid-20th century, Americans could see their politicians and other public figures regularly on 15-minute evening news shows. Two television networks - NBC and CBS - expanded their evening news shows to 30 minutes only months before Kennedy went to Dallas.
Television had already played a significant role in Kennedy's career, beginning with the first televised live debate with vice president Richard Nixon in September 1960, which was viewed by more than 70 million people.
Those who heard the debate on radio generally gave the night to Nixon; those who saw it on television generally agreed that Kennedy won. It was all about image - the young, vigorous Massachusetts Democrat projecting cool confidence in contrast to the sweating, pasty-skinned Republican vice president.
Kennedy won the election by a very thin margin, overcoming such issues as his relative youth, minimal experience, his Catholicism and being the pampered son of privilege.
Once in office, he held 64 televised press conferences - the first time live press conferences were held in the White House.
He addressed the nation in times of crisis, notably when Soviet missiles were being installed in Cuba, and to stump for his policy and legislative initiatives, including the creation of the Peace Corps, the plan to land a man on the moon before the end of the decade, and the need for federal civil-rights legislation.
It may be difficult for younger Americans to know what it was like that weekend in 1963. On Friday afternoon, children were sent home from school, parents wept and the world seemed frozen in a daze of shared disbelief. The networks broke into regular programming and tried first to ascertain what had happened and then tried to make sense of it all for viewers.
The public knew first that Kennedy had been shot, but no one could believe it would be fatal. That didn't happen in the US. Anchorman Walter Cronkite confirmed, in an everlasting moment of raw, emotionally staggering television, that it could and that it had.
Television news seemed to grow up immediately that afternoon. For the rest of the weekend and on into the following week, there was only one thing on TV, and it was the aftermath of the assassination.
We saw Jacqueline Kennedy returning to Washington, her suit still stained with her husband's blood. We saw the new president, Lyndon Baines Johnson, deliver his first official statement. He'd wanted his remarks to be televised live.
And on Sunday, November 24, we saw Jack Ruby's arm thrust forward from a group of reporters and onlookers and we saw Lee Harvey Oswald's body fold inward as his mouth formed an "Ohhhh".
The same day, Americans saw JFK's casket transported from the White House to the US Capitol on a horse-drawn caisson.
That weekend was momentous for the nation and the world, and for television as well. The medium would become even more of a dominant source of information in the following years, bringing the Vietnam conflict into American living rooms, the marches and protests of the civil-rights movement, the killings of Robert F. Kennedy and Martin Luther King Jr, the dissolution of trust as a presidential administration crumbled in the wake of a so-called third-rate burglary, the assassination attempts on presidents Gerald Ford and Ronald Reagan, the space shuttle Challenger disaster, and 9/11.
For much of that time, breaking news meant broadcast news. Beginning with Challenger, it also meant cable news. Today, it also means social media. The media are more sophisticated, the imagery more immediate, ubiquitous and, of course, in colour.
We have become used to having tragedy in our living rooms or on our computer screens now. We still react, of course, but perhaps not the same way people reacted a half-century ago. You can only lose your innocence once, and that weekend in November, the US nation and the television media lost theirs. It was a dreadful price to pay.
