As investigators try to understand what led Dzhokhar and Tamerlan Tsarnaev to attack their adopted home city, they are looking carefully at one of the brother's connection to the far off region of Dagestan. YouTube videos posted by Tamerlan after his 2012 visit to the Russian province suggest a possible connection or relationship with Abu Dujana, an Islamic militant leader who was killed by the Russian army last Decemeber.

The older Tsarnaev brother left the United States for six months last year, and apparently spent part of that time Dagestan. The brothers' father currently lives in Dagestan's capital, Makhachkala, which was also home to Abu Dujana, who was believed to have links to larger separatist movements in the region, including Chechen terror groups. In December, Abu Dujana—also known as Gadzhimurad Dolgatov—and several others were killed by Russian security forces in a brutal firefight. (CNN has broadcast video of the battle that the Russians had released to prove both that Dolgatov was dead, and that his group was heavily armed and equipped at the time of the fight.) 

Tsarnaev's YouTube channel had linked to videos of online speeches by Dolgatov that have since been taken down. Authorities haven't yet established any direct link between Dolgatov and Tsarnaev and its possible that he never did meet with any terrorists while in Dagestan. According to the Daily Mail, during his trip there last year, Tsarnaev met several times with a low-level member of the local "underground" Islamic militant movement, but neither of them were ever questioned, even though he had already drawn the attention of Russian security services.

However, the video links could suggest that Tsarnaev was at least aware of and sympathized with Dolgatov's movement and perhaps could even have been inspired by his death. It may also have been a connection between the two that inspired authorities on both sides of the world to take an interest in Tsarnaev, leading to claims today that the FBI "dropped the ball" when tracking the potential terrorist.