Tamerlan Tsarnaev (FILE)
U.S. officials say investigators have found no evidence that a conservative Muslim friend of Tamerlan Tsarnaev had any connection to the Boston Marathon bombing.
Family members have said Tsarnaev grew up religiously apathetic, but hardened his Islamic views in 2008 or 2009 under the influence of a Muslim convert known to the family as "Misha."
It remains a mystery who, exactly, this person is. CBS News notes that Misha is an extremely common nickname in Russia, particularly as a shortened form of the name Mikael.
Tsarnaev's uncle, Ruslan Tsarni, said of the man to CNN: "This person just took his brain. He just brainwashed him completely."
Elmirza Khozhgov, once a brother-in-law of Tsarnaev, said Tsarnaev once introduced him to somebody by the name.
"It seemed to me that Misha had influence on Tamerlan," 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."
Tsarnaev soon became an ardent reader of jihadist websites and extremist propaganda, two U.S. officials said. He read Inspire magazine, an English-language online publication produced by al-Qaida's Yemen affiliate. He also apparently took an interest in "The Protocols of the Elders of Zion," the classic anti-Semitic hoax first published in Russia in 1903 that claims a Jewish plot to take over the world.
Two U.S. officials close to the investigation say the FBI has identified an individual believed to be Misha. They would not say whether the FBI has spoken to him, but say they've found no ties to the attack or terrorism in general.
The officials spoke on condition of anonymity because they were not authorized to discuss the case. Tsarnaev, one of two suspects in the bombing, died in a shootout with police.
CNN has more on the mysterious "Misha":
The Associated Press contributed to this report.