On the 15th of April, 2013 a horrific attack happened upon the Boston Marathon event, taking 3 lives and leaving hundreds injured. Two explosions were triggered, the first being on the finish line, the second just a 2 minute walk (near the First Republic Bank) before the finish line.
The map below indicates where the two explosions occurred.
Boston Marathon Finish Line, Boylston Street, Boston, MA, United States (More info)
Google Maps Co-ordinates: 42.349753, -71.078617