(CBS News) RUSSIA -- Slain Boston Marathon bombing suspect Tamerlan Tsarnaev spent much of last year in his homeland in southern Russia. Investigators want to know what he was doing there and who he was with.
When Tsarnaev returned to Dagestan - where he'd spent some of his teenage years - his relatives said it was a happy reunion.
But there were some differences according to his aunt. He'd quit drinking, grown a beard, and he'd found religion.
Patimat Suleimanova said her nephew Tsarnaev "was no fanatic".
"He was curious," she said, "We would talk about his commitment to religion, but it wasn't extreme."
Members of a mosque in Dagestan told CBS News Tamerlan Tsarnaev attended Friday prayers, but there was nothing unusual about his behavior.
One neighbor said Tsarnaev spent most of his visit helping his father to renovate a shop. What he did with the rest of his time is not known.
Dagestan - which borders Chechnya - is the center of a violent Islamic insurgency fighting for independence from Russia.
In 2010 Islamic militants bombed the Moscow subway system during rush hour, killing 38 and wounding more than 60.
And while there's no evidence that Tsarnaev joined these militant groups, the violence would have been impossible to ignore.
Analyst Maria Lipman has studied Chechnya since the 1990s.
"You hang around. You hang around with people your age, with probably young men and I think it doesn't take too long before you discover that some of those young men are probably involved in something that is unlawful activities," she said.
But yesterday, the most feared terrorist group in the region said it had nothing to do with the marathon bombing - and it had never made contact with Tsarnaev.
(Left: A tale of two brothers: Tamerlan and Dzhokhar Tsarnaev)
A Russian Government official who is familiar with the investigation told CBS News they were looking to see if there were any direct contacts or links between Tamerlan Tsarnaev and any of the known terrorist or militant groups in the region during his time in Dagestan.
At this early point in the investigation, they say they have found none.