Boston Marathon Explosion

In this undated photo provided by Robin Young, Dzhokhar A. Tsarnaev poses for a photo after graduating from Cambridge Rindge and Latin High School. Tsarnaev has been identified as the surviving suspect in the marathon bombings. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, April 19, 2013. (AP Photo/Robin Young)