The story of Tamerlan and Dzhokhar Tsarnaev contains many elements of a classic immigrant experience: driven from a troubled corner of the world, finding refuge in the United States, and chasing dreams similar to those that have motivated generations of newly minted Americans.

Only this story now includes setting bombs that tore apart their adopted home, authorities say.

Until Monday's bombing of the Boston Marathon, the Tsarnaev brothers were largely assumed to have embraced American life. Now they are suspected of planting the two improvised explosives that killed three and injured dozens in one of the worst terrorist attacks on American soil.

"It's hard to fathom that someone that I knew, saw every day, would be capable of something like this," said Idia Irele, who attended Cambridge Rindge and Latin School with Dzhokhar Tsarnaev.

For complete coverage, visit NBC News

“He was a very respectful young man,” said John Curran, a boxing coach who helped Tamerlan Tsarnaev during the time he won a 2009 New England Golden Gloves title. “That’s what is so mind blowing about this whole situation.”

They spoke, as many bewildered acquaintances did, in the hours after the brothers were named as suspects, triggering a massive police manhunt that culminated Friday. Tamerlan Tsarnaev, a 26-year-old husband and father, died Friday morning with an explosive device reportedly strapped to his chest after leading police on a wild car chase and allegedly killing one police officer. Dzhokhar Tsarnaev, 19, was arrested late Friday after he was found hiding in a trailered boat behind a house in Watertown.

By dawn the streets of Boston and its suburbs were put on lockdown with residents told to remain at home, as throngs of police officers in battle gear combed the usually busy, but now tense and quiet, neighborhoods. Transit was closed down and the Boston Red Sox game was canceled as the hunt dragged into evening.

Gradually, the brothers' story emerged, pieced together by authorities, relatives and friends.

Asylum from war

Tamerlan Tsarnaev was an outspoken athlete who spoke three languages, played the piano, studied engineering, was a devout Muslim and aspired to represent the United States at the Olympics.

Dzhokhar Tsarnaev was a introspective but popular star of the Cambridge Rindge and Latin School wrestling team who won a city-sponsored scholarship to attend college.

The brothers were part of a family refugees who fled the war-torn Chechnya region of Russia and immigrated to America a decade ago. Located in the North Caucasus region of Russia, Chechnya has been riven by wars between separatist militants and the Russian government. Chechen rebels have been involved with terrorist attacks in Russia, but not, to anyone’s knowledge, in the West.

Their family—two parents, sisters and two brothers—fled the region and in 2003 ended up in America.

“They immigrated and received asylum,” Ruslan Tsarni, the brothers’ uncle, told reporters outside his home in suburban Maryland.

A seemingly nice kid

The brothers grew up in Cambridge, just outside Boston.

Dzhokhar Tsarnaev was a little withdrawn but nice to those who got to know him.

“He was a quiet and passive guy, well liked,” Ash Raful, a wrestling teammate who at one point looked up to Dzhokhar Tsarnaev, told the Today show.

He was also an extremely hard worker who made it to the state wrestling playoffs despite having only a couple years' experience with the sport, Ash said.

Deana Beaulieu said she'd known Dzhokhar Tsarnaev since the seventh grade. She, too, remembered him as a quiet boy who did little more than go to school and come home.

"You always have to be worried about the quiet ones I guess," Beaulieu said.

Robin Young, a Boston-area journalist whose nephew was friends with Dzhokhar Tsarnaev, described him as a "light, airy, beautiful, curly-haired kid" who'd attended the prom and won an academic scholarship.

"No one can believe that it's this young man," Young told Today.

In 2011, Dzhokhar Tsarnaev was granted a $2,500 scholarship from the City of Cambridge to continue his studies in college, the Boston Globe reported. He eventually enrolled at the University of Massachusetts-Dartmouth.

He became a naturalized American citizen on Sept. 11, 2012, according to documents obtained by NBC News.

Another former classmate, Sierra Schwartz, told Today that Dzhokhar Tsarnaev “was very normal."

“This was an incredible shock to everyone," Schwartz said.

On a Russian social media site, Dzhokhar Tsarnaev identified his religion as Islam and his priorities as career and money, according to NBC News.

The suspects' father, Anzor Tsarnaev, said in an interview from Russia with The Associated Press that his surviving son was "a true angel."

"Dzhokhar is a second-year medical student in the U.S. He is such an intelligent boy. We expected him to come on holidays here," the father said.

He added: "They were set up, they were set up! I saw it on television; they killed my older son Tamerlan."

Some of Dzhokhar Tsarnaev's acquaintances said they didn't know until Friday that he had an older brother.

Olympic dreams

Tamerlan Tsarnaev became a legal permanent resident in 2007, officials said. He spent a couple years studying at Bunker Hill Community College in Boston while pursuing his dream of a boxing career. He last took classes there from 2006 to 2008, school officials told the Associated Press.

He was the subject of a photographic profile in 2010 in a Boston University student magazine in which he said he’d taken time off from engineering studies to focus on the Golden Glove competition. He described himself as a devout Muslim who didn’t smoke or drink. “I don’t have a single American friend,” he was quoted as saying. “I don’t understand them.”

Tamerlan Tsarnaev said he hoped to use boxing as a path to citizenship, by way of qualifying for the Olympics.

His coach, John Curran, who met him in 2008, described Tamerlan Tsarnaev as a gifted athlete who often performed complicated gymnastic moves — tumbles, handstands — in the gym. He spoke three languages and played the piano.

Curran said that Dzhokhar Tsarnaev sometimes accompanied his older brother to the boxing gym, but did not fight. He seemed introverted, especially in comparison to his older brother's outgoing nature.

"He was like a puppy dog following his older brother," Curran said.

Tamerlan Tsarnaev ended up winning a New England Golden Gloves title, Curran said. They lost touch in 2010.

An aunt told reporters on Friday that Tamerlan Tsarnaev had a wife and young daughter.

The wife's parents, who live in Rhode Island, released a statement saying they never knew Tamerlan Tsarnaev.

"Our hearts are sickened by the knowledge of the horror he has inflicted," the in-laws said.

Travel to Russia questioned

Tamerlan Tsarnaev traveled to Russia last year, staying six months before returning in July 2012, according to travel records obtained by NBC 4 New York.

That travel is now of interest to investigators, who want to know if he received any terror training while he was overseas, NBC 4 New York reported.

Among the many questions they are trying to answer is whether the brothers acted alone or were part of a larger conspiracy or had connections to foreign militants.

NBC News reported that counter terrorism officials were examining possible links with the Islamic Jihad Union of central Asia.

In August, after he returned from Russia, Tamerlan Tsarnaev appears to have created a new YouTube account. Five months ago, a new playlist was added to the account, called 'Terrorists.' The playlist included two videos, both of which have been deleted.

A family's shame

Ruslan Tsarni, the brothers’ uncle, grew visibly angry when he was asked about what may have motivated them to commit such a horrific crime.

Tsarni said he hasn't seen his nephews in years, and could only speculate.

“Being losers,” he said. “Not being able to settle themselves. Hating everyone who did.”

Tsarni went on to say that had brought shame on their family and the Chechen people.

Cathy Rainone, WNBC's Brynn Gingras and The Associated Press contributed to this report.