Two explosions occurred near the finish line at the Boston Marathon on April 15, about four hours after the start of the race. At least three people were killed, and more than 170 were wounded.
Boston Marathon Explosion
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Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, April 15, 2013.
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A woman is comforted by a man near a triage tent set up after explosions went off at the 117th Boston Marathon, April 15, 2013.
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A Massachusetts state police officer guards the area containing the medical tent, rear, following an explosion at the 2013 Boston Marathon, April 15, 2013.
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An unidentified Boston Marathon runner leaves the course crying near Copley Square following an explosion, April 15, 2013.