Boston-4/15/13-  Seconds after the first bomb exploded, Carlos Arredondo(left) climbs over the barricades on Boylston Street to get to the injured on the sidewalk near the finish line at the Boston Marathon.

Boston-4/15/13- Seconds after the first bomb exploded, Carlos Arredondo(left) climbs over the barricades on Boylston Street to get to the injured on the sidewalk near the finish line at the Boston Marathon.