Two bombs exploded about 10 seconds and 100 yards apart at about 2:50 p.m. Monday April 15th 2013 in Boston's Copley Square, near the finish line of the Boston Marathon. An 8-year-old boy, a 29-year-old woman and a Boston University graduate student from China were killed, and more than 170 were injured. The explosions occurred four hours into the race and two hours after the winners had crossed the finish line, but thousands of runners were still on the course.