The dramatic arrest of Boston Marathon bombing suspect Dzhokhar Tsarnaev Friday night brought the entire city of Boston a collective sense of relief, with crowds streaming into the streets to chants of USA. But the end of the manhunt was in many ways just the start of the process for investigators trying to piece together what may have motivated Tsarnaev, 19, and his older brother, Tamerlan, 26, who was killed by police early Friday morning. And details emerging over the first 24 hours since police captured the younger Tsarnaev in a backyard boat in Watertown, Mass., reinforce the growing perception that his older brother was the primary driver of the attack.

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Dzhokhar Tsarnaev, who was hospitalized in serious condition Saturday night from a gunshot wound, was by most accounts a smart, well-adjusted guy in high school. Three years ago, he won a $2,500 scholarship from the city of Cambridge when he was a senior at the prestigious Cambridge Rindge & Latin School. He even went to his senior prom — and seemed to enjoy it. Classmate Sierra Schwartz told the New York Times he was “accepted and very well liked.” But while he was a good student in high school, he suddenly started to struggle in college at the University of Massachusetts-Dartmouth, and a transcript obtained by the Times said he failed seven classes over three semesters. Still, even after Monday’s bombing, Tsarnaev returned to the UMass-Dartmouth campus, attending classes and socializing in the dorms, according to the Boston Globe.

On the other hand, the Tsarnaev family appeared to have long known something was wrong with Tamerlan, an unemployed, college dropout. Ruslan Tsarni, one of the Tsarnaev brothers’ uncles who lives in Montgomery Village, Md., argued in interviews with The Today Show and CNN that “outside influences” clearly “brainwashed” Tamerlan, specifically an Armenian man who also lived in Cambridge and recently converted to Islam. He started to notice Tamerlan’s transformation as early as 2009, he told NBC’s Savannah Guthrie:

His family was not the only ones to notice Tamerlan’s transformation. The Russian FSB intelligence service told the FBI in 2011 about information that he was a follower of radical Islam, two law enforcement officials said Saturday.

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According to an FBI news release, a foreign government said that Tamerlan Tsarnaev appeared to be strong believer and that he had changed drastically since 2010 as he prepared to leave the U.S. for travel to the Russian region to join unspecified underground groups.

The FBI did not name the foreign government, but the two officials said it was Russia. The officials spoke on condition of anonymity because they were not authorized to talk about the matter publicly.

The FBI said that in response, it interviewed Tamerlan Tsarnaev and relatives, and did not find any domestic or foreign terrorism activity. The bureau said it looked into such things as his telephone and online activity, his travels and his associations with others.

Tamerlan did indeed end up traveling to Russia for about six months in 2012; the father told the Times that he had gone there to renew his passport, but ended up staying longer. The question is whether something happened during this extended trip that gave Tamerlan the idea to carry out the bombing at the Boston marathon. “They have been framed,” the father told the Times.

The brothers’ mother, Zubeidat Tsarnaeva, also could not believe that the brothers came up with this plot on their own because they knew that the FBI had been on their trail for the past “three to five years,” according to an interview with Russian state TV news station Russia Today obtained by Reuters. ”And being a mother, what I can say is that I am really sure, I am, like, 100 percent sure, that this is a set-up,” she said.

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Women who knew Tamerlan’s wife Katherine Russell as early as 2008 and 2009 told NPR’s Lauren Sullivan that he always had a strange disposition. They say he became more “religious” around 2008 when he stopped drinking and smoking and forced Russell to “cover herself.” One friend said that she saw Russell wearing a hijab at a Whole Foods about a year ago and acting “fearful.” Another described Tamerlan as a short-tempered, very “controlling” and “manipulative,” person who would call Russell names, such as “slut” and “prostitute.” While Tamerlan was arrested for domestic assault and battery in 2009 – which may have prevented him from becoming a US citizen like his younger brother– Segal says that complaint involved a different woman.

Friends say Russell — who also had a three-year-old daughter with Tamerlan — distanced herself from her family, which may explain why the Russell family said they didn’t know Tamerlan well in a written statement handed to a reporter outside their North Kingstown, RI home Friday night: “Our daughter has lost her husband today, the father of her child…In the aftermath of the Patriot’s Day horror, we know that we never really knew Tamerlane Tsarnaev.”

Just as friends say Tamerlan had a lot of control over his wife, Tsarnaev’s family says he had a lot of control over his little brother. Peter Tean, 21, who was on the high school wrestling team with Dzhokhar, told the New York Times that Dzhokhar took up wrestling to be more like Tamerlan, a talented boxer, who competed in the Golden Gloves national Tournament in 2009: “He’s done these violent sports because his brother’s a boxer. He really loves his brother, looks up to him.” Tamerlan would even take Dzhokhar to Friday prayer, their father Anzor Tsarnaev told the Times. Neighbors also told the newspaper that they would often see the duo hanging out in the Cambridge area, where Dhzokhar had an apartment on Norfolk St.

(MORE: The Brother Bombers: Did Sibling Psychology Contribute?)

There was no immediate word Saturday on when Dhzokhar Tsarnaev might be charged and what those charges would be. The twin bombings killed three people and wounded more than 180.

The most serious charge available to federal prosecutors would be the use of a weapon of mass destruction to kill people, which carries a possible death sentence. Massachusetts does not have the death penalty.

U.S. officials said an elite interrogation team would question the Massachusetts college student without reading him his Miranda rights, something that is allowed on a limited basis when the public may be in immediate danger, such as instances in which bombs are planted and ready to go off.

The American Civil Liberties Union expressed concern about that possibility. Executive Director Anthony Romero said the legal exception applies only when there is a continued threat to public safety and is “not an open-ended exception” to the Miranda rule, which guarantees the right to remain silent and the right to an attorney.

The federal public defender’s office in Massachusetts said it has agreed to represent Tsarnaev once he is charged. Miriam Conrad, public defender for Massachusetts, said he should have a lawyer appointed as soon as possible because there are “serious issues regarding possible interrogation.”

Massachusetts Gov. Deval Patrick said Saturday afternoon that Tsarnaev was in serious but stable condition and was probably unable to communicate. Tsarnaev was at Boston’s Beth Israel Deaconess Medical Center, where 11 victims of the bombing were still being treated.