Ten Steps to Disaster S02 E04 Boston Marathon Bombing

April 15, 2013. Two explosions rock the Boston Marathon, killing three people and injuring over 260. The blasts are immediately identified as a terrorist act, but many questions remain. Who planted the bombs? Why did they do it? And most pressing of all: how did they pull off an attack at one of America's most celebrated events undetected? Through in-depth analysis and expert testimony, we list the missed opportunities, security failures, and other errors that allowed the devastating events to unfold before, during, and after the bombing.