As yesterday's dramatic manhunt for the last remaining Boston bomber unfolded, so too did more of the Tsarnaev brothers' history come out. And while friends say younger brother Dzhohkar seemed like a relatively "normal" teenager, descriptions of now-deceased older brother Tamerlan are more troubling: it turns out he was interviewed by the FBI just two years ago when the feds began to wonder if he had extremist ties.

Tamerlan, a skilled Golden Gloves boxer, reportedly had a difficult time settling into American life after arriving here in 2004, two years after younger brother Dzhokhar immigrated with their parents. The family struggled financially, with father Anzor Tsarnaev working sporadically as a mechanic, and Tamerlan dropped out of Bunker Hill Community College after only three semesters. In 2009, the same year he took part in the Golden Gloves tournament, he was arrested on a domestic assault and battery charge after allegedly assaulting a girlfriend (his father said he "hit her lightly," and told the Times that "[t]here were jealousy problems").

Later, Tamerlan, who had a green card but did not become an American citizen, married American woman Katherine Russell. They had a child together, she converted to Islam and, according to friends and neighbors, started dressing in traditional garb and left the house infrequently. And Tamerlan, who had a YouTube account featuring religious, radical videos and traveled to a Russian region rife with radical Islamic activity last year, also caught the attention of the FBI. A senior law enforcement official confirmed that they interviewed the elder Tsarnaev brother in 2011, after a foreign government asked feds to find out if he had ties to any extremist groups in Chechnya. The investigation yielded “no derogatory information.” "They said: We know what sites you are on, we know where you are calling, we know everything about you. Everything," Anzor Tsarnaev told the Wall Street Journal of the interview.

But the younger Tsarnaev seemed far more assimilated into American life than Tamerlan, and friends describe him as a "cool bro..an average dude" who liked rap music, skateboarding, wrestling and smoking marijuana. Dzhokhar was a student at UMass Dartmouth, with plans to become a dentist, and he played intramural soccer. "He was just an average kid,” Chris Baratta, a student at UMass who hung out with Dzhokhar a few times, told Boston.com. “Kind of quiet." Many people claiming to be friends with Dzhokhar said they couldn't believe he had ties to Monday's bombing, airing their shock on Twitter and even offering to testify for him.

Dzhokhar was only eight years old when his family moved to the United States from Kyrgyzstan and a year or so in Russia's Dagestan region; unlike his brother, he became a naturalized citizen last year. "His brother and family weren't really Westernized, but Dzhokhar was really integrated into our school community," a high school classmate of his told the Wall Street Journal. " He was a normal American kid."