Boston bombs: Unanswered questions
As specialist investigators wait to question Dzhokhar Tsarnaev in hospital, a number of questions about the Boston Marathon bombing are hanging in the air. These are some of the issues that investigators will grapple with in the coming days and weeks.
What was the motive?
Investigators have not offered a motive for the Boston attacks, and US President Barack Obama has urged people not to rush judgment about the suspects' motivations. But it remains the key question both for those seeking to understand on an emotional level why the bombings took place, and for the US authorities whose next steps it will shape. A picture has begun to emerge of the elder brother Tamerlan as someone embittered toward the US, interested in radical Islam and influential over his younger brother. Much has been made of the Tsarnaev brothers' ethnic Chechen background and also of the elder brother's six-month trip to Dagestan last year. But despite what appear to be hints at a motive, the authorities have still not been able to question the man who can explain it.
Did the pair act alone?
One of the key questions for investigators is whether the pair had financial or logistical help from other people. The bomb-making equipment used for the two devices that killed three people and maimed so many more was rudimentary and inexpensive. Experts have pointed out that the two suspects had forced a man whose car they hijacked to withdraw $800 from a bank's cash machine, perhaps suggesting they were not well-resourced, and had no apparent plan to escape their home city. But their decision to target such a high profile event as the Boston Marathon has rung alarm bells, and prompted some to ask whether there could there still be remnants of a cell operating in the US. However the authorities say the immediate threat ended with the killing and capture of the brothers.
Did the FBI miss opportunities to stop the bombing?
The FBI interviewed Tamerlan Tsarnaev about his links to extremism in 2011 at the request of "a foreign government", thought to be Russia, which stated it was based on information he was a follower of radical Islam and was about to travel abroad to "join unspecified underground groups". The FBI says it found no evidence of a threat, but requested more information. The following year Tamerlan spent six months in the restive Russian republic of Dagestan. Correspondents say that as the euphoria over the capture of Dzhokhar fades, the questions over the FBI's role will grow.
Is the brothers' ethnic Chechen background significant?
Although the two men grew up in the US, their formative years will have been dominated by two Russian military campaigns in the predominantly Muslim region of Chechnya in the 1990s that led to tens of thousands of deaths. The offensives prompted an influx of Islamists into Chechnya and Moscow has always argued that the rebels were part of a global jihadist movement linked to al-Qaeda. Ever since the brutal crackdown on Chechnya's breakaway aspirations in the 1990s, rebels have seen Russia as a legitimate target but have not considered the West as a target. And Chechnya's pro-Kremlin President Ramzan Kadyrov insists Chechens have no interest in attacking the US. "Any attempt to make a connection between Chechnya and the Tsarnaevs is in vain," he said. However Russia has linked Chechen rebels to fighting in Afghanistan in recent years, so US authorities will want to know if Tamerlan Tsarnaev or his brother had formed contacts with the rebels.
Why did the two brothers attack the country that brought them up?
Perhaps the hardest question for authorities to answer will be what President Obama himself posed: "Why did young men who grew up and studied here as part of our communities and our country resort to such violence?" In a 2010 photo essay, Tamerlan was quoted as saying he did not have a single American friend. A neighbour, Albrecht Ammon, told of an argument he had with the elder brother about US involvement in Iraq and Afghanistan a few months ago. "He had nothing against the American people. He had something against the American government," the neighbour said. Dzhokhar Tsarnaev was considered by friends to be well integrated in US society. A former schoolmate described him as very popular and with a kind soul. An uncle, Ruslan Tsarni, is convinced that the University of Massachusetts student was "used" by his elder brother.