Gonzo Journalist Hunter S Thompson claimed to have found conclusive proof that the Twin Towers were brought down by explosives and was in the process of writing a book on his findings. 
One evening during a phone conversation, he nervously remarked to a freind that he was sure the CIA were going to try and kill him before he could get the information out.
He was found dead the next evening.

The official explanation was that he had committed suicide by shooting himself - in the side of the head (with a silenced weapon) - while he was half way through writing his column for the next day - while also on the phone to his wife - and while half way through completing the most important work of his life...