The evolution of Tamerlan Tsarnaev from aspiring Olympic boxer to apparent self-radicalized jihadist may have been influenced by a friend in Cambridge, Massachusetts.
"It started (in) 2009. And it started right there, in Cambridge," Tsarnaev's uncle Ruslan Tsarni said from his home in Maryland.
"This person just took his brain. He just brainwashed him completely."
Tsarni would not identify his nephew's friend. But he was so concerned about the acquaintance that he called a family friend in the Cambridge area to investigate.
"I said, 'Listen, do you know what is going on with that family? With my brother's family?' Then he says ... there is a person, some new convert into Islam of Armenian descent," Tsarni told CNN's Shannon Travis. "Armenians, I have no intention to say anything about Armenians. It's a neighboring region with North Caucasus," the same area where the Tsarnaev family also hails from.
Tsarnaev's mindset leading up to the bombings at the Boston Marathon may never be fully known. He was killed after a shootout with police last week.
His younger brother, Dzhokhar, remains hospitalized with an array of gunshot wounds. He has been charged with using and conspiring to use a weapon of mass destruction resulting in death, as well as one count of malicious destruction of property by means of an explosive device resulting in death.
Dzhokhar has been communicating with investigators in a limited fashion. He has indicated that his older brother, not any international terrorist group, masterminded the deadly attack, a U.S. government source said.
The preliminary interviews with Dzhokhar suggest the two brothers fit the classification of self-radicalized jihadists, the source said. But the official noted that information from the preliminary interviews needed to be scrutinized.
Dzhokhar has also cited the U.S. wars in Afghanistan and Iraq as motivating factors behind last week's blasts that killed three and wounded hundreds more, a U.S. government official said.
The suspects' uncle said Tamerlan was clearly the leader between the two brothers.
"Dzhokhar is being used by his older brother. (Tamerlan) used him as his -- not even accomplice -- as some kind of instrument," Tsarni said.
At 26, Tamerlan was seven years older than Dzhokhar. Friends say Dzhokhar followed his big brother around like a puppy.
And with their father in Russia, the older brother may have become a father figure to the 19-year-old these past few months. At 6-feet-3, Tamerlan was, by many accounts, an intimidating presence with increasingly strong convictions about society and religion in recent years.
Tsarni said he was shocked by the explosions and how his nephews may be involved.
"Tamerlan is off now," the uncle said. "There is no obedience and respect to his own father. That concerns me big time."
-- CNN's Jake Tapper and Wayne Drash contributed to this report.
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