This combination of undated photos shows brothers Tamerlan Tsarnaev, 26,...

This combination of undated photos shows brothers Tamerlan Tsarnaev, 26, left, and Dzhokhar Tsarnaev, 19. The FBI says the two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence on April 19, 2013. Credit: AP

People who know the brothers suspected of the Boston Marathon bombings remembered them as polite, scholarly and athletic.

But while some friends and family of Dzhokhar Tsarnaev, 19, and Tamerlan Tsarnaev, 26, expressed utter disbelief that the young men would kill innocents and spark a massive manhunt that shut down the nation's sixth-largest metropolitan area, others said the young men had shown signs of alienation from American society.

The brothers recently posted on Russian social-networking sites, according to a law enforcement source, including a video on the younger brother's page encouraging jihadists to travel to Syria to fight the government there. The older brother was quoted in a photo essay a few years ago, saying, "I don't have a single American friend, I don't understand them."

Last night, in the suburb of Watertown, Mass., police finally apprehended Dzhokhar Tsarnaev. Older brother Tamerlan Tsarnaev died early yesterday morning after a chase that authorities said began after the pair killed a Massachusetts Institute of Technology police officer.

A New Jersey woman who identified herself as their sister said she hadn't seen them for years and was dumbfounded by the pair's actions.

"They were great people. I never would have expected it," she told reporters through the door of her West New York, N.J., apartment. "They are smart -- I don't know what's gotten into them."

Dzhokhar and Tamerlan Tsarnaev, who had lived in the United States for years, both were registered to vote in Massachusetts, according to public records, a privilege given only to U.S. citizens by birth or naturalized.

The brothers were exceptional athletes -- the elder a boxer of Golden Gloves championship caliber with Olympic dreams, the younger an all-star wrestler in high school -- and both graduated high school and went on to college.

Tamerlan Tsarnaev, according to reports, had studied engineering at Bunker Hill Community College in Boston, but took a leave of absence to train for the Golden Gloves Tournament of Champions in Salt Lake City in 2009.

Dzhokhar Tsarnaev, currently a student at University of Massachusetts-Dartmouth, attended high school at Cambridge Rindge and Latin. In 2011, his senior year, he was named an all-star wrestler, according to printed reports.

That same year, he contacted Brian GlynWilliams, a professor at UMass-Dartmouth, to learn more about his Chechen heritage. He had been assigned to write an essay on his ethnic background, and "he seemed totally uninformed" about Chechens and Chechnya, Williams said in a telephone interview Friday.

The Tsarnaev brothers' father, Anzor, in a telephone interview with The Associated Press from the Russian city of Makhachkala, said that Dzhokhar was studying medicine and called him "a true angel."

"He is such an intelligent boy," the father said. "We expected him to come on holidays here."

Maret Tsarnaeva, a Toronto woman who identified herself as the suspects' aunt, laid out the family's history in an interview Friday.

She said the brothers' father had been persecuted in his homeland and persuaded authorities in the United States to let him into the country as a refugee in 2002, first coming with his wife and Tamerlan, leaving his three other children with a brother, she said.

The brothers' father later returned to Chechnya and his wife joined him there a few months ago, she said. He had "high expectations" of his oldest boy, Tsarnaeva said: "He knew he was smart. He knew he could use his potential."

Their mother, Zubeidat Tsarnaeva, told CNN that she thought her sons had been set up by authorities, adding that she was close to both of them and would know if they harbored extremist views.

"My oldest son . . . never talked about terrorism," she said. He had become increasingly religious in the recent past, she said, and "he never told me he would be on the side of jihad."

Law enforcement sources and recent acquaintances had more foreboding descriptions.

A source said Tamerlan Tsarnaev went to Russia last year and returned to the U.S. six months later. Both Tamerlan Tsarnaev and his younger brother were struggling financially, having difficulty fully acclimating to American society and becoming embittered, a law enforcement source said.

Albrecht Ammon, 18, of Cambridge, said he was neighbors with Tamerlan Tsarnaev and his wife and daughter. He said he and Tsarnaev jousted about religion and foreign policy.

He "definitely opposed the American government," Ammon said, adding that he "thought the Bible was a cheap copy of the Koran."

Ammon also said the older brother had said America was a colonizing power trying to take over Africa and the Middle East, and that most of the innocent people killed in Iraq and Afghanistan died at the hands of American soldiers.

Tsarnaeva, the suspects' aunt, acknowledged some difficulty, singling out Tamerlan.

Though he was married and had a young daughter -- "He was really happy about his daughter," she said -- "Somehow, he did not find himself yet in America, because it's not easy."

The London Daily Mail quoted the parents of Tamerlan Tsarnaev's wife, Katherine Russell, 24, as saying their "hearts are sickened" by the bombings. According to the article, the couple has a young daughter, and Russell converted to Islam for her husband.

With Mackenzie Issler, Robert E. Kessler and Victor Manuel Ramos

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