One was a pot-loving student, the other had begun exploring Islam in an effort to turn his life around. So how did Dzhokhar and Tamerlan Tsarnaev end up at the Boston Marathon finishing line with a willingness to kill?
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The moment of the explosion at the Boston Marathon Photo
5:39PM BST 27 Apr 2013
As they hunched over the twisted bomb parts and pieces of shrapnel, some still bloody from where they cut through flesh, the FBI technicians were finding a grimly familiar pattern.
Elbow pipes from common plumbing systems. Specially-picked rounded bearings and nails of a short but disfiguring length. Gunpowder, cannibalised from the kind of …show more content…
The FBI is now desperately trying to pinpoint at what stage between 2009 and Tamerlan's death during the police shootout nine days ago his growing religious zeal spilled over into violent extremism.
Two areas remain particularly crucial to investigators. The first is Tamerlan's relationship with a shadowy Armenian convert to Islam identified so far only as "Misha". Accounts of how the portly, red-bearded man fits into Tamerlan's story vary widely.
What is agreed is that the pair appear to have met in 2008 or 2009 and the young Chechen soon began to defer to Misha's knowledge of Islam, spending hours at the family's kitchen table in Cambridge listening to him speak.
Ruslan Tsarni (Getty Images)
The bombers' uncle, Ruslan Tsarni, depicts Misha as a Rasputin-like figure and a part-time exorcist who "took [Tamerlan's] brain" and said that his presence soon became a source of tension within the family.
But Tamerlan's mother, Zubeidat Tsarnaeva, paints a more benign picture of a "very gentle" man who helped the entire family move closer to their faith.
"There was nothing not to like about him," she said. "We were just embarrassed in front of him when he was in our house praying and we weren't."
Which version the FBI believes