A part of this investigation must involve looking at the overwhelming evidence of pre-knowledge going back decades. I've listed the evidences in:
https://steemit.com/conspiracy/@irishidentitaire/9-11-synchronicity-foreshadows-and-predictions-part-1
Remember that pilot episode of the X-Files spin-off, "The Lone Gunmen"? The storyline is the 9/11 scenario.