(CNN) -- The evolution of Tamerlan Tsarnaev from aspiring Olympic boxer to apparent radical jihadist may have been influenced by a friend in Cambridge, Massachusetts.
"This person just took his brain. He just brainwashed him completely," Tsarnaev's uncle, Ruslan Tsarni, told CNN from his home in Maryland, describing the friend as an Armenian convert to Islam.
While Tsarni did not give the friend's name, The Associated Press reported that other members of Tsarnaev's family said the friend goes by the name "Misha."
Asked about those reports, Elmirza Khozhgov, a former brother-in-law of Tsarnaev, told CNN Tsarnaev once introduced him to someone by that name who was an Armenian convert. He said he was not told Misha's full name.
"It seemed to me that Misha had influence on Tamerlan," apparently encouraging him to give up boxing because it "is violent," Khozhgov told CNN's Wolf Blitzer.
"Tamerlan told me that he quit boxing and music because Misha was teaching that it's not good in Islam to do those things."
"Misha" taught Tsarnaev "things that would make Tamerlan go away from the people and go more into the religion," Khozhgov said, but "I didn't witness him making him radical."
Khozhgov added that he has not spoken with Tsarnaev or with the younger suspect in the Boston Marathon bombings, Dzhokhar Tsarnaev, since 2010. And even then, "We didn't talk for a long time."
Tamerlan Tsarnaev "seemed normal" at the time, he added. "He only told me he goes to the mosque often and he's doing community work at the mosque."
Officials have not responded to requests for comment on someone named "Misha." Lawmakers briefed Tuesday on the investigation told CNN they had not heard of anyone by that name.
The Islamic Society of Boston told CNN Wednesday that so far no one in its network reported knowing a "Misha" who fit that description.
"We are looking for him," said spokeswoman Nichole Mossalam.
Uncle called a friend to investigate
Tsarni, Tsarnaev's uncle, told CNN he was so concerned about someone brainwashing his nephew 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.
"It started (in) 2009. And it started right there, in Cambridge," Tsarni said of the friendship.
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 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 Tsarnaev has been communicating with investigators in a limited fashion. He has indicated that his older brother, not any international terrorist group, conceived the deadly attack, a U.S. government source said.
The preliminary interviews with Dzhokhar Tsarnaev 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 Tsarnaev 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 Tsarnaev 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 Tsarnaev was seven years older than Dzhokhar. Friends say Dzhokhar followed his big brother around like a puppy.
And as their father is in Russia, the older brother may have become a father figure to the 19-year-old these past few months. At 6-foot-3, Tamerlan Tsarnaev 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 Shannon Travis, Jake Tapper, Brian Todd and Wayne Drash contributed to this report.