FBI From left: Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev in Boston, Mass., on April 15, 2013.

Two weeks after the Boston marathon bombings killed three people and injured hundreds more, one suspect is dead and another is in custody and charged with a capital crime. The basic outlines of the story of the Tsarnaev brothers seem clear. Yet recent news reports and comments from members of Congress underscore that critical questions about their alleged crimes remain unanswered, complicating the emerging debate over what lessons America should draw from the horror on Boylston Street. Here are the most pressing:

Did They Really Act On Their Own? During his initial interrogation, Dzhokhar Tsarnaev reportedly said that he and his brother Tamerlan acted alone, motivated by anger over America’s wars in Iraq and Afghanistan, and that they learned how to construct their bombs online. Officials have disclosed no evidence to the contrary, but there are hints of a more complex plot. By some accounts, their bomb detonators–exploded via remote controllers for toy cars–required a sophistication that the Tsarnaev brothers didn’t otherwise show when, for instance, they failed to wear disguises to the marathon site, or when they carelessly allowed a hostage to escape. “There was some outside counsel to these individuals on how to build and how to detonate,” House Intelligence Committee Chairman Mike Rogers told Fox News last week, although a national security source also told Fox that the toy-car detonator is not a known al Qaeda technique.

Meanwhile, investigators continue to explore a six-month trip Tamerlan took to Russia last year, and whether he met with Islamist rebels in the country’s troubled republic of Dagestan. House Homeland Security Chairman Michael McCaul suggested to NBC yesterday that the Tsarnaev brothers might have had a foreign “trainer”: “And the question is, where is that trainer or trainers?” McCaul asked. “Are they overseas in the Chechen region or are they in the United States?”

How Much Does Vladimir Putin Know? Some lawmakers believe the Russian government is being coy about its intelligence on the Tsarnaev family. “I think they do know more than they’re telling us,” Democratic Rep. Adam Schiff, a member of the House Intelligence Committee, told CNN yesterday. Those suspicions have hardly been allayed by this weekend’s revelation that Russia informed U.S. officials only recently about recorded phone conversations, including one in which Tamerlan Tsarnaev and his mother, Zubeidat Tsarnaeva, discussed “jihad.”

Those conversations were the basis for the warning by Russia’s Federal Security Service (FSB) to the FBI about Tamerlan Tsarnaev two years ago. After the FBI’s three-month investigation sounded no alarms, however, Russia didn’t respond to the bureau’s request for more information.

“There’s got to be a basis for why [Russia] went up on her electronically or why they went up on one of her affiliates or associates,” Schiff told CNN, referring to Tsarnaev’s mother. “We haven’t received that information from the Russians.” It’s possible Russia is worried about exposing its intelligence operations. It’s also possible the Russians just don’t like to share with us. As Rogers noted on ABC’s “This Week” yesterday, “You have to remember the FSB is a hostile service to the FBI and the CIA.”

Did U.S. Intelligence Officials Fail to ‘Connect the Dots’ Again? A more dogged pursuit of leads and better intelligence sharing could have prevented the September 11 attacks, and some lawmakers now wonder if the same goes for Boston. The FBI investigated Tamerlan in 2011 after Russia’s initial warning that he’d grown enchanted by Islamic radicalism, but the bureau closed its file on him after finding no “derogatory” information. Even if the FBI had no legal grounds to continue surveilling Tsarnaev without more specific information, however, some critics suggest that local law enforcement could have kept an eye on him.

At the federal level, meanwhile, critics are asking whether intelligence agencies should have perked up when Tamerlan returned from a six-month trip to Russia last year. Republican Senator Lindsey Graham of South Carolina calls it a “system failure” that the Department of Homeland Security didn’t notify the CIA and FBI about Tamerlan’s trip. “I am now saying to my fellow citizens, 11 years after 9/11 clearly our system is not working,” Graham told CNN last week. But Homeland Security chief Janet Napolitano told Congress last week that her department didn’t notify the FBI because the bureau’s alert on Tsarnaev had expired months before, leaving DHS with no impetus to share word of the trip. Some members of Congress weren’t assuaged, and have also wondered why the FBI team in Boston didn’t get more prodding from headquarters.

Who Is ‘Misha’ and Where Is He? Tamerlan’s relatives say that his sharp turn toward Islam, while perhaps fostered in part by disappointment over his stalled boxing career, was encouraged by a man the Associated Press describes as a “mysterious radical”–a bearded man known only as “Misha.” “This person just took his brain. He just brainwashed him completely,” Tsarnaev’s uncle, Ruslan Tsarni tells CNN. Misha is a Muslim convert who urged Tamerlan to quit boxing, stop studying music, and adopt a sharply anti-American worldview. The Associated Press and other news outlets have thus far been unable to locate Misha, an older, heavyset Armenian native with a reddish beard whom Tamerlan reportedly met in 2008 or 2009. According to the Daily Beast, the feds have now identified “Misha,” though it’s unclear whether they have spoken to him yet. They are no doubt eager to. With so many questions about the terror in Boston still lingering, investigators are desperate to talk to anyone who might have answers. Update: Last night Christian Caryl reported meeting with a man in Rhode Island who he says is Misha; the man says he “wasn’t [Tamerlan’s] teacher, and that he is “cooperating entirely” with the FBI.

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