I just found out about the mysterious death of Dr. David Graham:
One year before the attacks of 9/11, a Louisiana dentist named Dr. David Graham met two of the alleged 9/11 hijackers at the home of a Pakistani businessman in Shreveport, LA outside Barksdale Air Force base. He became suspicious of the two men who were introduced to him as "medical students" because they couldn't speak English. Fearing that they might be involved in sabotage at the nearby Air Force base, he reported his sighting to the FBI. They assured him there was nothing to worry about.
This was before 9/11. Later, after the attacks of September 11th, when he realized that the two men he had met were among the 19 individuals identified as hijackers he reported the sighting once again to the FBI, Secret Service, Justice Department and members of Congress. Strangely no one in authority seemed interested. He was even warnedby the FBI agents he had repeatedly spoken with that his health might be endangered if he persued his plan to write a book about the meeting. He never got a chance to publish his book. He was poisoned while traveling through Texas. The authorities ruled his lingering death from ingesting anti-freeze as a suicide. His friends and co-workers believe he was murdered. When he was asked who he thought might have poisoned him, he said, "the FBI."