He said Tamerlan referred to the Bible as a "cheap copy" of the Quran, and that many of this country's wars "are based upon the Bible — how it's an excuse to invade other countries."
"He had nothing against the American people," Ammon said. "He had something against the American government."
Dzhokhar, on the other hand, was "real cool," Ammon said. "A chill guy."
An elder at the Islamic Society of Boston Cultural Center, the largest mosque in New England, said Tamerlan occasionally attended Friday prayer services at the mosque in the past year and a half.
About three months ago, around Martin Luther King Day, Tamerlan stood up and interrupted the imam during the sermon, said Anwar Kazmi, a board member of the Islamic Society. The imam compared the slain civil rights leads to the Prophet Muhammed, drawing objections from Tamerlan, Kazmi said.
Mosque leaders later sat down with Tamerlan and discussed his rant, said Kazmi, who said Tamerlan returned to future services and had no further outbursts.
While his older brother was railing about religion and world politics, Dzhokhar seemed more interested in the HBO series "Game of Thrones" and other television shows.
"Breaking Bad taught me how to dispose of a corpse," he tweeted on Jan. 16, referring to the popular AMC series about a dying chemistry teacher who turns to cooking methamphetamine to leave a nest egg for his family.
He did tweet about religion, but they were hardly the words of a hard-core zealot.
"This night deserves Hennessy a bad b---- and an o of weed," he wrote on Nov. 17. "the holy trinity"
On Nov. 29, he wrote: "I kind of like religious debates, just hearing what other people believe is interesting and then crushing their beliefs with facts is fun." And on Jan. 15: "I don't argue with fools who say Islam is terrorism it's not worth a thing, let an idiot remain an idiot."
However, he acknowledged in another message around Christmas that the "Brothers at the mosque either think I'm a convert or that I'm from Algeria or Syria."
Fox said it's not unheard of for the younger person in a crime team to be the dominant personality. But he said it's rare.
"In this case, the older brother is the one that seems to have become religious and drawn to Islam," Fox said. "The older brother dropped out of school ... whereas the younger brother, it was all positives."
But, he said, "the age factor is critical here."
Tamerlan was a fairly gifted boxer, but he preened about fighting prowess that often fell far short. His younger brother seemed content to be part of a team.
Marvin Salazar was two years older than Dzhokhar when they attended Community Charter Schools of Cambridge, where they played intramural soccer together. He was impressed by the younger boy's smarts and drive, but noted that while Dzhokhar was very fast, he wasn't the kind of kid who needed to showboat and score goals.
"I remember he told me he liked to play midfield," the 21-year-old said. "He's the guy who sets everybody up for the plays. He's one of the most important people."
He was also on his high school wrestling team.
Tamerlan once said he had no American friends. His brother had lots of them, but fellow students at UMass-Dartmouth say he also hung out with some Russian speakers.
On March 14, 2012, Dzhokhar tweeted: "a decade in america already, i want out" That same day, he added, "im trying to grow a beard"
Dzhokhar became naturalized last September, federal officials told the AP. His older brother had a green card but may have been thwarted in his quest for U.S. citizenship by an assault charge, his father told The New York Times.
If Tamerlan recorded his thoughts, they have not yet surfaced — at least publicly. His brother left a trail on the Internet, although in an Aug. 7, 2012 tweet, he called himself a "heavy sleeper and a great liar"
In March, Dzhokhar tweeted: "Evil triumphs when good men do nothing." A week and a half earlier, he reminded his followers, "Never underestimate the rebel with a cause."
The day of the bombing, he wrote: "There are people that know the truth but stay silent & there are people that speak the truth but we don't hear them cuz they're the minority"
Tsarni is confident authorities will find that Tamerlan was his younger brother's "mentor."
"Dzhokhar, of course, was looking up at him," he said.
But their body language the day of the bombings seems to suggest at least a partnership of equals.
In one of the now infamous photos the FBI released to the public in hopes of tips, the older brother has his head down, the visor pulled low over his face as if he's trying to hide. Dzhokhar, by contrast, has his white baseball cap turned backward, revealing his entire face, his chin is thrust confidently into the air.
Associated Press videojournalist Joseph Frederick contributed to this report.
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