Excerpt:
Months before the 2013 terror attack on the Boston Marathon, accused bomber Tamerlan Tsarnaev posed in front of a black flag often associated with jihad with a fellow worshiper at a Boston-area mosque, according to an FBI report obtained by ABC News.
The FBI report, which did not include the photo, describes Tsarnaev and his friend Khairullozhon Matanov as "seated in front of a black flag with a sword and a shadada phrase," referring to the Muslim statement of faith, and adds that the photo was taken "at the mosque." Similar flags have become symbols of jihad, used by al Qaeda and al Qaeda-linked extremist groups.
The FBI had been warned by Russian intelligence in 2011 that Tsarnaev may have become radicalized, but the bureau dropped its inquiry months before the photo was taken because it said it "did not find any terrorism activity."