People in Boston continue to struggle to understand the motive of the bombings and the murder of a police officer on the MIT campus. At Wednesday's memorial for the slain officer, Vice president Joseph Biden spoke with angry contempt of the Tsarnaev brothers. "Two twisted, perverted, cowardly, knock-off jihadis here in Boston," he said.
One lingering mystery lies in what changed for Dzhakhar Tsarnaev, who spent most of his childhood and formative years in America schools, and was widely described as easy going and well liked. Just last year, on September 11, in a patriotic ceremony on the floor Boston's TD Garden, the University of Massachusetts student and casual soccer player sat among 2,500 immigrants and swore his allegiance to the United States, becoming a naturalized citizen of the United States.
Seven months later, authorities say he told FBI agents that he and his brother planted bombs along the route of the revered sporting event and killed a police officer. The reason he gave, according to authorities, was that Muslims are at war with the US.
Michele McPhee is a Boston-based freelancer who is a frequent contributor to ABC News.