1. SPECULATION

    Dzhokhar Manipulated by Brother?

    This combination of undated photos shows Tamerlan Tsarnaev, 26, left, and Dzhokhar Tsarnaev, 19. The FBI says the two brothers and suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left Tamerlan dead and Dzhokhar still at large on Friday, April 19, 2013. The ethnic Chechen brothers lived in Dagestan, which borders the Chechnya region in southern Russia. They lived near Boston and had been in the U.S. for about a decade, one of their uncles reported said. (AP Photo/The Lowell Sun & Robin Young)

    Tamerlan and Dzhokhar Tsarnaev. (AP)

    Now that the two Boston marathon bombing suspects have been captured, one dead, the other alive and in serious condition, speculation swirls around what motivated Tamerlan and Dzhokhar Tsarnaev, brothers and Chechnyan immigrants, to attack a massive crowd of innocent people. What information is available about the two brothers suggests that Tamerlan, the older brother, may have influenced Dzhokhar to participate in the bombing. Tamerlan, a 26-year-old boxer who'd once aspired to box for the U.S. Olympic team, seemed to struggle with life in America more than his younger brother. Tamerlan was still trying to become a citizen at the time of the bombings, held back by a domestic violence complaint from a girlfriend. Dzhokhar, 19, whose parents and friends find his involvement in the bombings impossible to believe, looked up to his older brother.