Once the FBI learned the identities of the two brothers today, the FBI reviewed its records and determined that in early 2011, a foreign government asked the FBI for information about Tamerlan Tsarnaev. The request stated that it was based on information that he was a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States for travel to the country’s region to join unspecified underground groups.

In response to this 2011 request, the FBI checked U.S. government databases and other information to look for such things as derogatory telephone communications, possible use of online sites associated with the promotion of radical activity, associations with other persons of interest, travel history and plans, and education history. The FBI also interviewed Tamerlan Tsarnaev and family members. The FBI did not find any terrorism activity, domestic or foreign, and those results were provided to the foreign government in the summer of 2011. The FBI requested but did not receive more specific or additional information from the foreign government.

One of the Boston bombing suspects set off alarm bells among his family a year ago during a trip here to visit relatives, ABC News has learned.

According to a family member, Tamerlan Tsarnaev was kicked out of his uncle’s house because of his increasingly extremist views…

Members of Congress, however, say those six months last year were a turning point in Tamerlan Tsarnaev’s radicalization.

“When he came back he starting posting more radical jihadist YouTube videos and started becoming more of a fundamentalist Muslim,” Rep. Michael McCaul, chairman of the House Homeland Security Committee, told ABC News Friday.

LAURA SULLIVAN, BYLINE: Well, these women were close friends and roommates of Tamerlan’s girlfriend, Katherine Russell, and they knew him for several years while they were in college. They described Tamerlan as very controlling and very manipulative of their friend. They say he was combative and angry. He would often call her names and insult her. He would call her a slut and a prostitute, and they remember fights that they would get into where he would fly into rages and sometimes throw furniture or throw things…

He was arrested for domestic assault and battery, but it was of a different woman. They had an on-again, off-again relationship, Katherine Russell and Tamerlan, and that was at a different period in about 2009, but over the years that they knew Tamerlan, and they knew him through Katherine, they say that, you know, he had really changed a lot. That he had started off in 2007 sort of partying with them – he would smoke, and he would drink – and then sometime around 2008, they say he became very religious, and he stopped smoking, and he stopped drinking, and he stopped going out with them. And it was at that point that they say he demanded that Katherine also convert to Islam and cover herself…

They said that when they first met him, he didn’t seem particular political in any way, but that starting in about 2008 and 2009, they describe it as having an extremist point of view, that he started talking about being angry with the government, and he said that he felt that Islam was under attack.

Online, it appears, Tamerlan toyed with extremism. A YouTube account created in Tamerlan Tsarnaev’s name in August 2012 includes in one playlist a video dedicated to the prophecy of the Black Banners of Khurasan, which is apparently embraced by Islamic extremists.

In another video, featured on a playlist entitled “terrorists,” a speaker holds an assault rifle and wears camouflage fatigues while flanked by armed men wearing masks.

“There will always be a group of people who will stick to the truth, fight for that truth,” the speaker says in Russian with an accent common to the Caucasus region that includes Chechnya. “And those who won’t support them will not win.”

The Globe could not confirm that the user was the same person as the bombing suspect who was killed in a shoot-out.

There are signs that the brothers showed interest in the conflict in Syria, which has drawn al Qaida fighters and other militants from across the Muslim world and Europe, according to a U.S. counterterror official. Like others interviewed for this story, the official requested anonymity because he was not authorized to discuss the ongoing case.

The brothers had viewed videos about the plight of Syrian Muslims, the official said. Syria is the latest hotspot on the world map of jihad. Holy warriors a decade ago were inspired by videos about brutal combat between jihadis and Russian troops in the brothers’ family homeland: the predominantly Muslim region of Chechnya, a breeding ground for al Qaida fighters in the late 1990s and early 2000s.

Tamerlan had viewed a video titled “I Dedicate My Life to Jihad,” according to a U.S. law enforcement official. The brothers also were apparently influenced by the online Inspire magazine, a slick English-language publication that plays a strong role in disseminating ideological tracts and bomb-making techniques to Western extremists, the U.S. counterterror official said.

“It’s like London, it’s like Madrid in the radicalization,” the counterterror official said. “These guys were produced by the international jihadist machine. The biggest thing is they were individuals willing to die. They were committed. There was interest in events overseas affecting Muslims. And a lot of Internet activity 2014 the things that everyone in the counterterror community worries about.”

Siblings have historically been viral vectors for one another’s risky behaviors. A girl whose older sister is a teen mom is six times more likely to become one herself. Alcohol consumption is twice as likely among kids with at least one sibling who already drinks; for smoking the risk increases fourfold…

In the current case, there were a few factors that probably nudged those risk figures higher. For one thing, the young men lived together. Proximity is a critical element in what psychologists call “delinquency training” among siblings. This is true for lower-grade risk behaviors like smoking or drinking, since a younger sibling, who typically picks up the habit later than an older one, must be able to observe and model the bad behavior—to say nothing of getting hold of the forbidden substances in the first place…

That comparatively minor misbehavior could offer a flicker of insight into the brothers’ crime if it was suggestive that a deeper sociopathic fire was burning. Typically, the real variable in criminal collaboration is not so much the blood relationship of the perps, but the interpersonal relationship—the influence of a compelling, charismatic personality on another, weaker one.

But should we think of the Tsarnaevs as a threat that was “homegrown”? Or “foreign”? Again, they are both. Both spent significant chunks of their youths in the United States. Especially in the case of Dzhokhar, who became a U.S. citizen on September 11, 2012, they seem to know little of their country of extraction. Both at least partially assimilated in the U.S. Some sources report that they were registered voters. Yet in their digital lives and their own words, they both identified themselves as Russians or Chechens first, displayed ambivalence or downright animosity to America, and seemed to feel that they could not adapt to or thrive in this country — a sense of being, in their uncle’s memorable phrase, “losers.” It would not be surprising to see evidence in the coming days and weeks that this alienation was causally wrapped up in the brothers’ radicalization. In that regard, we see Hasan again, but also Coloradan Anwar al-Awlaki and Sulayman al-Faris (formerly known as John Walker Lindh)…

Lastly, were the Tsarnaevs ideologues, evil, or “just nuts”? This might be the most complicated question. As with all the others, the best answer again is “all of the above.” This is speculative, but if early reports are borne out, we’ll see a portrait emerge of a dominant, pathological, and increasingly ideological older man who was the lead plotter and who had enlisted younger men as his accomplices and then wielded considerable psychological power over them. Here we see the murderous and perverted father-son dynamic of John Allen Muhammed and Lee Boyd Malvo, who in the fall of 2002 terrorized Washington, D.C., with a sniper rifle. That duo was a putrid mix of ideology, psychopathy, evil, and manipulation, and it would hardly be surprising if the full facts in the Tsarnaevs’ case reveal something much the same.

One or both of the brothers might well have been in touch with Chechen separatists, whose Web sites they were reportedly reading. They could even have been in touch with al-Qaeda. But I wouldn’t jump to that conclusion. Chechen terrorists have in the past been more anti-Russian than pro-Islam. They are not known for being anti-American.

Look, instead, at another possibility, one that is in some ways more disturbing than the convenient “foreigners who hate us” explanation. Although very little has been confirmed, the behavior of the Tsarnaev brothers looks less like that of hardened, trained terrorists and far more closely resembles the second-generation European Muslims who staged bombings in Madrid, London and other European cities. Educated and brought up in Europe, these young men nevertheless felt out of place in Europe. Unable to integrate, some turned toward a half-remembered, half-mythological homeland in search of a firmer, fiercer identity. Often they did so with the help of a radical cleric like the one the Tsarnaev brothers may have known. “I do not have a single American friend,” Tamerlan Tsarnaev reportedly said of himself. That’s the kind of statement that might have been made by a young Pakistani living in Coventry, or a young Algerian living in Paris.

We don’t expect to hear it from someone who grew up in Boston, a city that has taught generations of foreigners to become Americans in a country that likes to think of itself as a melting pot. But now it might be time to change our expectations. These terrorists are a lot less like the 9/11 attackers — or the Columbine attackers — and a lot more like the men known as the Tube bombers of London or the train bombers of Spain. Our response is going to have to be different — very different — as well.

It’s very weird to live in a society where mass death is important insofar as it serves the political needs of the dominant ideology. A white male loner killing white kindergartners in Connecticut is news; a black doctor butchering black babies in Pennsylvania is not. When the manhunt in Boston began, I received a bunch of e-mails sneering I was gagging for it to be the Muzzies just as hungrily as lefties were for it to be an NRA guy, a Tea Partier, a Sarah Palin donor. But, actually, I wasn’t. On Monday, it didn’t feel Islamic: a small death toll at a popular event but not one with the resonance and iconic quality the big-time jihadists like — like 9/11, the embassy bombings, the U.S.S. Cole. After all, if the jihad crowd wanted to blow up a few people here and there IRA-style they could have been doing it all this last decade.

On the other hand, it didn’t feel like one of those freelance bumblers — the Pantybomber, the Times Square Bomber — finally got lucky. It feels like something in between, something new. Is it just a one-off? Or a strategic evolution?

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“There certainly were mentors,’’ Tsarni said. “I was shocked when I heard his words, his phrases, when every other word he starts sticking in words of God. I question what he’s doing for work, (and) he claimed he would just put everything in the will of God. It was a big concern to me. He called me ‘confused’ when I started explaining to him, make yourself useful to yourself and to your family and maybe you’ll have extra to share with everybody else.

“It wasn’t devotion, it was something, as it’s called, being radicalized. Not understanding what he is talking (about). He is just using words for the sake of the words and not understanding the meaning of it.’’…

“He said there is someone who brainwashed him, some new convert to Islam,’’ Tsarni said. “I would like to stress (the acquaintance was) of Armenian descent.’’…

“It has nothing to do with Russia, (or) with Chechnya, which he had nothing to do with,’’ Tsarni said. “It started here.”

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