A Boston police officer wheels in injured boy down Boylston Street as medical workers carry an injured runner following an explosion during the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria at the marathon&#39;s finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts.  <span class=meta>(AP Photo&#47;Charles Krupa)</span>
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