Ruslan Tsarni of Montgomery Village, Md., said Tamerlan told him in a 2009 phone conversation that he had chosen "God's business" over work or school. Tsarni said he then contacted a family friend who told him Tsarnaev had been influenced by a recent convert to Islam.
Tsarni said his relationship with his nephew ended after that call.
As for Dzhokhar Tsarnaev, "he's been absolutely wasted by his older brother," Tsarni said. "I mean, he used him. He used him for whatever he's done."
Albrecht Ammon, a downstairs-apartment neighbor of Tamerlan Tsarnaev in Cambridge, said the older brother had strong political views about the United States. Ammon quoted Tsarnaev as saying that the United States uses the Bible as "an excuse for invading other countries."
The all-day manhunt Friday brought the Boston area to a near standstill and put residents on edge across the metropolitan area.
The break came around nightfall when a homeowner in Watertown saw blood on his boat, pulled back the tarp and saw a bloody Dzhokhar Tsarnaev hiding inside, police said. The homeowner called 911.
After an exchange of gunfire with police, Tsarnaev was seized and taken away in an ambulance.
Raucous celebrations erupted in and around Boston, with chants of "USA! USA!" Residents flooded the streets in relief four days after the two pressure-cooker bombs packed with nails and other shrapnel went off.
Michael Spellman said he bought tickets to Saturday's Red Sox game at Fenway Park to help send a message to the bombers.
"They're not going to stop us from doing things we love to do," he said, sitting a few rows behind home plate. "We're not going to live in fear."
During the long night of violence leading up to the capture, the Tsarnaev brothers killed the MIT police officer, severely wounded another lawman and took part in a furious shootout and car chase in which they hurled explosives at police from a large homemade arsenal, authorities said.
Chechnya, where the Tsarnaev family has roots, has been the scene of two wars between Russian forces and separatists since 1994. That spawned an Islamic insurgency that has carried out deadly bombings in Russia and the region, although not in the West.
Tamerlan Tsarnaev studied accounting as a part-time student at Bunker Hill Community College in Boston for three semesters from 2006 to 2008, the school said.
He was married with a young daughter. Dzhokhar Tsarnaev was a student at the University of Massachusetts Dartmouth.
As of Saturday, more than 50 victims of the bombing remained hospitalized, three in critical condition.