Boston bombs: CIA placed Tamerlan Tsarnaev on main US terrorism watch list So he didn't stay where he went, but he learned something where he went and he came back with a willingness to kill people. The State Department later clarified Mr Kerry's remarks, saying he was "simply expressing broad concern about radicalism rather than indicating any new information." US officials have not determined if 26-year-old Tamerlan Tsarnaev, who died last Friday in a police shoot-out, became radicalised in Russia. The FBI has already admitted it interviewed Tamerlan in 2011 after Russia raised concerns that he was becoming a follower of radical Islam, but found nothing "derogatory" against him and did not pursue the case. Last night Senator Saxby Chambliss, the vice-chairman of the Senate Intelligence Committee, claimed that Russia had actually warned US officials about Tsarnaev not once, but twice. Russian security services monitored Tamerlan during the five-month visit he made to the North Caucasus region of Dagestan in 2011-12, but found no reason to arrest him, a security source told AFP earlier this week. Mr Kerry's remarks came as it was claimed that Tamerlan reportedly fell under the sway of a mysterious Muslim convert who steered him to a severe brand of Islam. Under Misha's guidance, Tamerlan is said to have grown increasingly radical and turned to al-Qaeda-linked websites. "Somehow, he just took his [Tamerlan's] brain," said Ruslan Tsarni, his uncle.