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Massachusetts State Police officers walk in formation during the funeral procession for the slain Massachusetts Institute of Technology (MIT) police officer Sean Collier at St. Patrick's Church on April 23, 2013 in Stoneham, Massachusetts.
As Boston bombing suspect Dzhokhar Tsarnaev begins to answer questions from investigators, new details are emerging about the motivation behind the attack. The Tsarnaev brothers were said to have been operating alone, driven by religious fervor and were not aligned with any known international terrorist or military groups. The brothers were thought to have been radicalized in the US through the Internet and learned how to make bombs through an al Qaeda website.
How will investigators determine the motives behind the attack? Do we know what Tamerlan Tsarnaev did on his trip to Dagestan and Chechnya last year? Was he involved in the mysterious triple homicide in Waltham, Mass., in September 2011?
Mark Arsenault, reporter for the Boston Globe