The two brothers suspected in the Boston Marathon bombing came to the U.S. from Kyrgyzstan and Chechnya, a primarily Muslim region in southern Russia with a history of conflict and insurrection, according to ABC News.
One of the brothers, 19-year-old Dzhokhar Tsarnaev, who is still at large, arrived in 2002. He entered the country with his parents on what federal officials called a "regular visa" and was later granted asylum. He became a U.S. citizen with his father and mother on September 11, 2012, ABC News reported.
We don't know enough about the suspects to speak to their potential motivations.
In a general sense, however, the U.S. faces a serious challenge in integrating young people who come from war-torn nations, according to Stevan Weine, a researcher for the U.S. Department of Homeland Security and University of Maryland's START research center. He's worked on cases involving Somali youth who came to Minnesota as refugees, but then returned to their home country to carry out terrorist attacks.
"You have young people who grew up in a war-torn country and then who come to this country as kind of unformed youth, who have to struggle with questions of identity, questions of allegiance," he said. "Young people often don't get enough help from their parents or support in the community to figure those issues out."
Could the immigration system have somehow flagged these two brother as potential threats?
From what we know now, probably not. Families gaining legal status through asylum claims undergo scrutiny for potential links to terrorism, but a screening can't prevent someone from radicalizing later in life.
Even now, there's been no authoritative evidence that the suspects had any link to terrorists networks, or whether they might have been motivated by ideology.
The best chance of countering this type of attack, according to Weine, is a preventative approach.
Since 2011, the Obama administration has placed a new focus on trying to identify potential domestic terror threats before they are able to act, sort of like community policing, but for national security, according to Weine.
"They're still doing hard counter-terrorism, but they're also trying to do more of a community engagement and partnership approach," he said.
That means connecting with local organizations, faith groups and parents when there may be a concern about a young person. The concept is still relatively new, however.
"I think there's a good reason for applying those approaches to countering violent extremists, but we don't yet have enough experience to say it definitely works," Weine said.