FORTY-FOUR years ago today, a clothing company owner named Abraham Zapruder filmed the assassination of John F. Kennedy in Dallas. And for 44 years, most people have presumed that his home movie captured the assassination in its entirety. This presumption has led to deep misunderstandings.

The majority of witnesses in Dealey Plaza heard three shots fired. Lawmen found three cartridges in Lee Harvey Oswald’s nest on the sixth floor of the Texas School Book Depository. Yet Zapruder’s film captured only two shots clearly. As a result, the film has been scoured for evidence of another shot, presumably the first one fired at the president. Research has yielded contradictory findings.

But what if Zapruder simply hadn’t turned on his camera in time?

Zapruder’s 26-second movie has two distinct parts. Approximately seven seconds after he started filming from the north side of Elm Street, Zapruder stopped his Bell & Howell Zoomatic at frame 132 because only Dallas police motorcycles were driving by. He did not restart his camera until the president’s limousine was clearly in view. Consequently, Z 133 is the first frame to actually show the president’s Lincoln — a frame exposed several seconds after the car had made the sharp turn onto Elm Street from Houston Street — and, we believe, after Oswald had squeezed off his first shot.

Several witnesses saw a man firing from the sixth floor. No one’s recollection about the first shot was more precise, though, than that of a ninth grader named Amos L. Euins. He told the Dallas County sheriff, “About the time the car got near the black and white sign, I heard a shot.” As the above photograph from a December 1963 restaging shows, the president’s limousine would have passed a black and white sign before Zapruder restarted his camera (the ghost image here approximates the location of the Lincoln at the moment Zapruder started filming again).