Boston bombing suspect Tamerlan Tsarnaev appears to have posted and then removed a video of a jihadist leader who was later killed by Russian troops.
A CNN analysis of Tsarnaev's YouTube channel has established that one deleted video under a sub-heading "Terrorists" featured a militant named Abu Dujana, whose real name was Gadzhimurad Dolgatov. CNN has located a video clip of the footage in question.
Russian security services killed Dolgatov in December during an assault on an apartment in Makhachkala, the capital of the Russian Caucasus republic of Dagestan. Dolgatov led a small militant group in Dagestan that had links to the main Islamist militant group in the region, Imarat Kavkaz.
Tsarnaev created a YouTube channel in August 2012, shortly after returning from a visit to Russia. Two videos posted under a category labeled "Terrorists" were deleted, but it wasn't clear when or by whom.
Tsarnaev was in Russia in 2012 and spent some of his time in Makhachkala, where his father lives today. U.S. officials told CNN analyst Tom Fuentes on Sunday they have found no further connection between Tsarnaev and Abu Dujana, but the investigation into his activities overseas continues.
The 26-year-old Tsarnaev died early Friday in a gun battle with police. He and his 19-year-old brother Dzhokhar have been named the suspects in last week's double bombing at the Boston Marathon, which killed three people and wounded more than 170.
An analysis of Tamerlan Tsarnaev's social media accounts and the accounts of family members suggests he became increasingly radical in the last three or four years.
Imarat Kavkaz -- the "Caucasus Emirate," in English -- has its roots in the 1990s Chechen insurgency against Russia. It was founded in 2007 to bring together various jihadist groups fighting to create an Islamic state in the region.
Its overall leader is Doku Umarov, a veteran Chechen guerrilla who claimed responsibility for the the 2011 bombing of Moscow's international airport. According to a 2011 report by the Center for Strategic and International Studies, the Caucasus Emirate has significant ties to al Qaeda.
"The evidence of the Caucasus Emirate's integration into global Jihad is overwhelming. Umarov has repeatedly associated the Caucasus Emirate with the global Jihad," the study concluded.
Separately, a U.S. intelligence source told CNN that investigators are looking into whether Tsarnaev had any connections with the group. The source said Tsarnaev had several computer links to the group in his social media activities and investigators are looking into the possibility he may have received "operational plans" from this group.
In a statement in June 2010, the U.S. State Department's coordinator for counterterrorism, Daniel Benjamin, said Umarov posed threats to the United States and Russia and that his attacks "illustrate the global nature of the terrorist problem we face today."
Tsarnaev's YouTube channel had the address "muazseyfullah," which happen to be the names of two prominent militant leaders among Islamist groups in Russia's North Caucasus, an area that includes Chechnya and Dagestan. Seyfullah also translates as "sword of Allah."
It is possible that the account he created has at some point been interfered with, but there is no obvious sign of that.
One video talks about his beliefs, prayers and ablutions as a good Muslim. He speaks about leading a meaningful life; almost the very last word is "peace." Another video is in praise of Muslim women who pray and dress conservatively.
Part of it was narrated by Khalid Yasin, an African-American Islamist preacher based in Manchester in the UK. The video praises women for wearing the full Islamic veil.
Yasin's critics have accused him of calling for the death penalty for homosexuality, claiming the HIV virus was engineered by Western governments, denying al Qaeda's involvement in 9/11, and stating that it is impossible for a Muslim to have a non-Muslim friend. In one video viewed by CNN, Yasin called the Taliban "our brothers."
Another video posted suggests a growing Salafist viewpoint, one common to militant Sunnis such as the Taliban in Afghanistan. It includes remarks by a Salafist sheikh, Abdul Hamid al Juhani, and references to the Salafist "brothers" from Chechnya as well as the violence in Syria. It also includes inflammatory remarks against Sufi Muslims -- a frequent target of militant Sunnis.
Another video on Tsarnaev's YouTube channel features a militant preacher, Feiz Muhammad, with a considerable online following. The video does not include overt jihadist sentiments, but the sermons of Muhammad -- a firebrand Lebanese-Australian preacher -- openly sympathize with al Qaeda's worldview.
"The war on terrorism is nothing but a war on Islam and on Muslims," he said in one widely available video, calling Americans "pigs" and "evil." In another tape, he urged young Muslims to become martyrs. His videotapes can be found on the websites of several U.S.-based groups, including the Islamic Thinkers Society and Revolution Muslim, both out of New York.
According to one former Islamist radical who spoke to CNN, Feiz Muhammad has been careful to keep his sermons within legal "red lines" and preaches openly in Australia.
The only video Tsarnaev posted with a strongly jihadist theme appears to have been reposted on his YouTube page four months ago, about the "emergence of the black flags from the promised land of Khorasan," a reference by jihadists to parts of Afghanistan.
The fact that Tsarnaev posted any Islamist-related material on his YouTube site has intrigued terrorism analysts. Al Qaeda and other terrorist groups have instructed recruits to fly below the radar screen and not to do anything to attract attention from authorities.
There are other aspects of Tsarnaev's life that suggest growing religiosity. His father, speaking from the Russian republic of Dagestan on Friday, said Tamerlan was religious but in a peaceful way. And one of his aunts, Maret Tsarnaev, who lives in Canada, said she believed he had become more religious in the past two years.
"Just recently, maybe two years ago, he started praying five times a day, which is, I don't see anything bad in it," she said.