On August 16, 2001, Moussaoui was arrested by Harry Samit of the FBI and INS agents in Minnesota and charged with an immigration violation. Materials itemized when he was arrested included a laptop computer, two knives, flight manuals pertaining to Boeing's 747 aircraft, a flight simulator computer program, fighting gloves and shin guards, and a computer disk with information about crop dusting.
Some agents worried that his flight training had violent intentions, so the Minnesota bureau tried to get permission (sending over 70 emails in a week) to search his laptop, but they were turned down. FBI agent Coleen Rowley made an explicit request for permission to search Moussaoui's personal rooms. This request was first denied by her superior, Deputy General Counsel Marion "Spike" Bowman, and later rejected based upon FISA regulations (amended after 9/11 by the USA Patriot Act). Several further search attempts similarly failed.
Ahmed Ressam, the captured al-Qaeda Millennium Bomber, was at the time sharing information with the US authorities, in an effort to gain leniency in his sentencing. One person whom he was not asked about until after 9/11, but whom he was able to identify when asked as having trained with him at al-Qaeda's Khalden Camp in Afghanistan, was Moussaoui. The 9/11 Commission Report opined that had Ressam been asked about Moussaoui, he would have broken the FBI's logjam. Had that happened, the Report opined, the U.S. might conceivably have disrupted or derailed the September 11 attacks altogether.
Zacarias Moussaoui - Wikipedia, the free encyclopedia