Most American intelligence reports point to one mastermind behind the attack: Osama bin Laden, head of the Al Qaeda Islamic terrorist group, thought to be hiding out in Afghanistan.
目前美國政府的多項情報，均將這次事件的主謀，指向目前躲藏在阿富汗的阿拉伯裔回教激進組織首領奧薩瑪・賓・拉登。