Keys to Boston attack could lie half a world away in restive region of Russia

The building, No. 50, that members of the Tsarnaev family call home sits on a seemingly quiet street in Makhachkala. The capital of Dagestan, a semi-autonomous republic in southern Russia, borders the Caspian Sea on one side and on the other overlooks the Caucasus Mountains.

For a time in 2012, Tamerlan Tsarnaev stayed here with his parents. He shopped at stores in Makhachkala, prayed at a local mosque.

What authorities want to know is whether it was here that Tamerlan learned, or perhaps was inspired, to kill.

The 26-year-old can’t give an answer: He was killed after a shootout with U.S. authorities in Watertown, Massachusetts – 5,500 miles from Makhachkala – early Friday.

Days earlier, authorities say, he and his 19-year-old brother, Dzhokhar – who is in a Boston hospital – blew up two bombs at the finish line of the Boston Marathon. Three people died and scores were wounded in that attack.

FBI agents spent Wednesday in the Dagestani capital talking with Tamerlan and Dzhokhar’s parents, according to an official in U.S. President Barack Obama’s administration. The U.S. investigators were joined by members of Russia’s Federal Security Service, human rights activist Kheda Saratova said.

That “conversation” ended Wednesday evening, the suspects’ mother, Zubeidat Tsarnaev, told Saratova.

It’s unclear what came of the parents’ talk with U.S. and Russian authorities, though both parents had publicly insisted that their sons are innocent. But information has come out suggesting how Tamerlan Tsarnaev might have been influenced by his trip half a world from his Cambridge, Massachusetts, home.

While Dagestan may be picturesque in many respects, it’s also been home to violence and civil unrest. That includes gun and bomb attacks targeting security services, including a suicide bombing at a police checkpoint that left 12 dead and dozens wounded while Tsarnaev was believed to be here.

After returning from his months-long visit to Russia, Tsarnaev created a YouTube channel that included two videos (since deleted) under a category labeled “Terrorists.”

Analysis by CNN and the SITE Intelligence Group has uncovered a screen grab from one of those videos featuring members of Imarat Kavkaz, a potent militant Islamist group in the north Caucasus, which includes Chechnya and Dagestan.

Tsarnaev also appears to have posted and removed a video of a militant named Abu Dujan, a jihadist leader who was later killed by Russian troops.

Did Tsarnaev interact with Abu Dujan during his time in southern Russia? Authorities haven’t publicly said anything on that point, either way.

Videos linked to his group show how to prepare homemade explosives from almost anywhere.

Askhabali Saurbekov, the police chief in the Dagestani town of Kizilyurt, said Abu Dujan met with foreigners before his death. This group included men, like Tsarnaev, who were of Chechen origin.

“They met to exchange their bandit experience,” Saurbekov said.

CNN’s Nic Robertson and Nick Paton Walsh reported from Makhachkala; Greg Botelho wrote this story from Atlanta.