Friends and family of the brothers who authorities say planted the bombs at the Boston Marathon struggled to explain Friday the actions of young men who lived, studied and played in the very community they are suspected of attacking.

Tamerlan Tsarnaev, 26, killed in a shootout with police, was a boxer and father who had created a YouTube channel called "Terrorists." A neighbor said he spoke of hating America.

Dzhokhar Tsarnaev, 19, captured late Friday, was a wrestler and college student who friends say volunteered in a "Best Buddies" program for kids with learning disorders.

David Mijares said he had been friends in high school with Tamerlan Tsarnaev, and had coached Dzhokhar Tsarnaev in junior varsity soccer at Cambridge Rindge & Latin School, a public school near Harvard University in Cambridge.

"I just wonder who influenced them, because this wasn't of their making, they didn't just suddenly change," Mijares said.

A man who lived in the same Cambridge neighborhood as the brothers and speaks Russian said the older one told him "he was upset with America because America was in Afghanistan and other Muslim countries." The man, who declined to give his name, added, "Should I have called someone to tell them this guy doesn't like America? I'm having second thoughts."

The brothers were ethnic Chechens born in Kyrgyzstan, a central Asian republic that was part of the former Soviet Union. The family had sought refuge from fighting in Chechnya, said a Russian official. The family then moved for a short time to Makhachkala in Dagestan, next to Chechnya, a mainly Muslim Russian republic that fought a war with Russia marked by terrorist attacks in Moscow and Beslan.

The family then came to the U.S. as refugees, said a law enforcement official, and was granted asylum.

Their aunt, Maret Tsarnaev of Toronto, told Canada's CTV the two were "very normal men," but also said Tamerlan Tsarnaev "seemingly did not find himself yet in America because it's not easy," the Los Angeles Times reported.

Tamerlan Tsarnaev's YouTube channel, created in August 2012, has religious overtones, as well as links to lighter fare, such as sites for "Vasya Oblomov," a satirical music project by Russian musician Vasily Goncharov.

Seven months ago, he created channels, one of which has been removed by YouTube, called "Terrorists" and "Islam." He cached videos about Russians converting to Islam, including one who turned to Shiism, a choice he seemed to denigrate. He also included inspirational videos of scholars who spoke about Islam and how the religion inspires believers and cleanses them of their sins.

The two brothers were named by a national security official as suspects in the bombings that killed three people and wounded more than 170 on Monday near the finish line of the Boston Marathon. Although born outside the U.S., they had been in the country for several years.

The FBI in 2011 interviewed Tamerlan Tsarnaev, acting at the request of an unidentified foreign government, a U.S. law enforcement source said on Friday.

But the FBI's dealings with Tamerlan Tsarnaev did not produce any "derogatory" information, and the matter was put "to bed," said the source, speaking on condition of anonymity.

The men's father, Anzor Tsarnaev, in a phone interview from Makhachkala, told the Times Friday his sons were innocent. "I will never believe my boys could have done such a terrible thing," he said. "I have no doubt they were set up."

Tamerlan Tsarnaev, a one-time Golden Gloves boxer, was killed in a shootout with police late on Thursday. Dzhokhar Tsarnaev was the target of a massive manhunt on Friday, extending from the Boston suburbs to the Connecticut border, where state police lined the highways, watching for a suspect vehicle.

The first thing that came to Mijares' mind when he saw the pictures was a one-hour drive that he and Tamerlan took together to register to compete at the Golden Gloves.

"During that drive, we spoke on a personal level. He spoke to me about his background, about why he was here," said Mijares, also a boxer. "He said it was scary and a lot of people were getting killed [in Chechnya]. He said Russia was taking over Chechnya and Chechnya didn't want to be a part of Russia."

He said that he and Tamerlan met in 2005 or 2006.

From what Mijares could tell, he was Tsarnaev's closest friend. He said they developed a bond through boxing and because they were both born in foreign countries. Mijares was born in Mexico.