A former FBI informant, Elie Assaad, has told ABC News that the agency blew a chance to stop 9/11 ringleader Mohamed Atta. Assaad says he first became suspicious of Atta in early 2001, when he infiltrated a small mosque outside of Miami. Assaad now says he’s a “million percent positive” the 9/11 attacks could have been stopped if the FBI had pursued his lead on Atta, but that the agency instead told him to focus on two smaller targets whose cases were easier to crack. "I was right, I was 100 percent right," Assaad says. When he learned that Atta was a 9/11 hijacker, Assaad says he was “very upset, angry” and that he cried.