Forty years ago, Dr. Martin Luther King, Jr. was shot down. The alleged assassin [was] a small time criminal on the run. Some of Dr. King's closest aides believe the full story has yet to be told. From his first days in the civil rights movement, Dr. King lived under the shadow of death - his house bombed in the Montgomery bus boycott, followers killed in Birmingham and Selma. He was stabbed once in Harlem at a book signing. Dr. King's electrifying speech at the March on Washington in August of 1963 had made him the ... the FBI's nightmare, according to the official paper trail. They called him in one of the FBI memos released later the most dangerous Negro." Pulitzer Prize winner David Garrow ... discovered thousands of these memos while writing his book, "The FBI and Martin Luther King." The memos show an FBI obsessed. Director J. Edgar Hoover sent Attorney General Robert Kennedy [the] warning [that] communists were pulling Dr. King's puppet strings. Fellow minister Ralph Abernathy discovered an FBI bug while speaking at an Alabama church. Hoover ... called Reverend King "the most notorious liar in the country" in a rare 1964 press conference. When Dr. King won the Nobel Prize, the FBI mailed an anonymous package to Dr. King's office [containing sexually explicit recordings along] with an ominous note. There was nothing nervous about him that last day in Memphis. "I'm not worried about anything. I'm not fearing any man," King said. He probably never even heard the shot.