They dressed like typical American teenagers, enjoyed playing sports and strived to fit in after arriving in the United States with their family from the southern Russian province of Dagestan a decade ago.
The schoolmates, teachers and neighbors of Dzhokhar and Tamerlan Tsarnaev said they saw little sign of radicalism - or anything extraordinary - to explain why the ethnic Chechen brothers would allegedly carry out the twin bombings that killed three people and wounded 176 at the Boston Marathon on Monday.
Tamerlan, 26, who dreamed of Olympic boxing glory and appeared to have become a more observant Muslim in recent years, was killed in a shootout with police late on Thursday. Dzhokhar, 19, who was a high school wrestler, was captured by police Friday night after a manhunt that virtually shut down Boston.
Twenty-four hours after the initial gunfight, the physical journey of the pair from Russia to Cambridge, Massachusetts, is fairly well-documented. But the psychological journey that might have led them to carry out the worst bomb attack on US soil since the plane hijackings on Sept. 11, 2001, is largely an enigma.
Exactly what motivated the pair to carry out the worst bomb attack on US soil since the plane hijackings on Sept. 11, 2001, remains a mystery.