BOSTON - APRIL 15: Women desperate to hear from loved ones can't enter the scene at Boylston and Mass. Ave. after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by Bill Greene/The Boston Globe via Getty Images)
People turn to social media to express their feelings of shock, sadness and horror after the Boston Marathon bombing.
One teen talks about the number of tragedies she's seen in her lifetime, while another runner says the bombings have not changed his dreams of running in the Boston Marathon.