Tamerlan Tsarnaev, 26, has been identified as the man killed during a huge manhunt launched in the early hours of Friday.
A YouTube account that appears to have been run by Tsarnaev includes a playlist devoted to "terrorism", including one video in English titled The Emergence of Prophecy: The Black Flags from Khorasan. He also maintained a playlist devoted to Islam and one devoted to Timur Mutsuraev, a Chechen singer who sang of the republic's battle for freedom from Russia.
Tsarnaev's background is murky. A teacher at School No 1 in Makhachkala, the capital of Dagestan, said that the Tsarnaev family lived briefly in the republic before moving to the United States. They had previously lived in Kyrgyzstan, in central Asia, she said.
Alvi Karimov, a spokesman for Ramzan Kadyrov, the leader of Chechnya, said that the family had lived in Kazakhstan, which maintains a large Chechen minority. The Tsarnaevs "moved to a different region of the Russian Federation from Chechnya many years ago", he told the Interfax news agency.
Tsarnaev appears to have been a competitive boxer, according to a photo report by photographer Johannes Hirn, who photographed Tsarnaev in 2010. Tsarnaev told the photographer that he was born in Chechnya and had been living in the US for five years.
"I don't have a single American friend, I don't understand them," Tsarnaev said.
He also appeared to support Chechen independence: "Unless his native Chechnya becomes independent, Tamerlan says he would rather compete for the United States than for Russia," one caption reads.
Tsarnaev presents himself as a devout Muslim, saying he had given up drinking and smoking. "I'm very religious," he said, explaining why he doesn't take his shirt off while training. The photographs were taken at the Wai Kru Mixed Martial Arts centre in Allston, Massachusetts (MA). The report says Tsarnaev was a student at Bunker Hill Community College in Charleston, MA.
In 2009 Tsarnaev was reportedly arrested for assaulting his girlfriend.
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