With the capture of bombing suspect Dzhokhar Tsarnaev, the investigation of the Boston Marathon attacks has shifted from a manhunt to the preparation for a prosecution and a quest to answer the question that most mystifies millions of onlookers: Why?
Federal officials believe that Mr. Tsarnaev, a 19-year-old Massachusetts college student, set off the twin explosions April 15 with his brother, Tamerlan Tsarnaev, 26, who was killed in a shootout two nights ago with police outside Boston.
The surviving brother, now reported to be in stable but serious condition at a Boston hospital, could face federal terrorism charges punishable with the death penalty. He could also face murder charges from Massachusetts prosecutors.
Many legal experts see the prosecution’s case as an unusually strong one. The evidence that has surfaced, according to news reports, includes bomb-making equipment at the apartment where the brothers lived, eyewitness testimony from one of the surviving victims, and video, photos, and forensic evidence from the marathon-day crime scene.
There’s also the fact that the two brothers exchanged gun fire with police and, according to some news reports, admitted to the owner of a car they hijacked that they were the marathon bombers.
But big questions remain, notably about their motivation and whether others aided their effort or concealed their plans.
That may explain why federal law enforcement officials did not read Miranda rights to Dzhokhar Tsarnaev when he surrendered on a property in Watertown, Mass. Although almost all people arrested in the US are read these rights, such as the right to remain silent and the warning that anything they say can be used in a court of law, exceptions can be made in cases where public safety is an imminent concern.
By not reading the rights, officials have greater ability to seek information from Tsarnaev. That leaves some risk that information they glean won’t be admissible in court. Some legal experts argue that Miranda rights should have been read to Tsarnaev promptly.
So far, much of the speculation about motives centers on the tug-and-pull between two influences on the brothers: Their connections with their heritage in violence-torn Chechnya, with its brand of jihadist militancy, and their possible feelings of displacement as immigrants in the United States.
Another facet of the story appears to be the question of how much Dzhokhar was following his older brother as a role model. Some friends of Dzhokhar – whom his incredulous father has described as an “angel” – have said the college student closely followed his brother in some ways.
An uncle of the brothers, Ruslan Tsarni, has said he grew concerned about Tamerlan Tsarnaev after a 2009 phone conversation during which Tsarnaev said he had chosen "God's business" over work or school. Tsarni said he then contacted a family friend who told him Tsarnaev had been influenced by a recent convert to Islam, according to the Associated Press.
Tamerlan Tsarnaev, who for a time was an aspiring boxer, was quoted in a 2010 Boston University photo essay as saying, "I don't have a single American friend. I don't understand them."
The brothers had been in the US for about a decade, but retained an interest in their homeland, Chechnya.
According to an ABC News report Saturday, Tamerlan Tsarnaev alarmed some family members with his religious views when he visited Russia in 2012. A relative, who said he wanted to remain anonymous to avoid offending other family members, said the young man had been radicalized in the US before the 2012 trip.
That doesn't mean the Tsarnaev’s Chechen ties are irrelevant to the case, some terrorism experts say. They say many Chechens have come to view their struggle against the Russian government as part of a global war between Islam and the West. If the Tsarnaev brothers identified with that view, in part based on their ethnic identity, it could have been a factor opening the door to violence in Boston.
At this point, the emerging details about their lives are still a tapestry that merely hints at possibilities, rather than confirming clear-cut motives.