Did a bomb explode at the Boston Marathon?

Two explosions were heard near the finish line, 13 seconds apart at 2:49 p.m. EDT on Boylston Street in Copley Square. Spectators and runners were injured and many were taken to medical tents set up nearby to help tired runners. The bombs were pressure cooker bombs made by Dzhokhar and Tamerlan Tsarnaev. The blasts killed 3 people and injured 264 others.