WhoWhatWhy: "Must Watch Video JFK Motorcade and Odd Secret Service Behavior", WhoWhatWhy YouTube Channel, 11 June 2013.
In this fascinating video - a little under three minutes in length - we see footage of JFK's Secret Service agents apparently being instructed to abandon the president's car prior to the assassination. Particularly striking is the reaction of the agent on the right: his behaviour seems to indicate that he simply cannot understand what's going on.
Image: "Portrait Photograph, President John F. Kennedy. White House, 07/11/1963" : US National Archives and Records Administration, ARC Identifier 194255, [Public Domain]; resized, cropped.