Bomb Suspect Calm as First Blast Ripped Apart Boston Marathon

Bomb Suspect Calm as First Blast Ripped Apart Boston Marathon

Charles Krup/AP Photo

While the crowd around him was seized with alarm and bewilderment, Tsarnaev calmly but rapidly began moving away from his knapsack. Ten seconds later, it exploded, driving nails and BB pellets into spectators near the storied race’s finish line.