President John F. Kennedy was riding in a motorcade through the streets of Dallas when a gunman fired from a window of a nearby building. Stunned onlookers ran for cover as the president's driver sped toward the hospital. The young leader could not survive his terrible wounds, meaning Lyndon Johnson would take over as president. Police quickly tracked down Kennedy's killer, but his troubling background and puzzling behavior raised questions that seemed impossible to answer. Although Kennedy's life had been cut short, his presidency and his assassination changed the country in ways still felt today.