the other problem is that these e-mails are occurring just days before the anniversary of 9/11. everybody was concerned that we had a major problem on our hand as. >> he was more or a lone wolf. how did authorities become aware this plot existed. >> didn't know he was there. he was living colorado at the time. he had traled to pakistan. trained in an al-qaeda training camp. gotten explosives training in an al-qaeda training camp and made it back into the united states and didn't know who he was. that in an of itself was nerve racking and in this story tonight, you're going hear how it unfolds and how the national security agency played a very important role on a small tip that allowed this whole thing to kind of kick into action and the scary thing and the good thing about this is it showed how across agencies our intelligence services kind of rounded up in