Guide to the bombing at the Boston Marathon BOSTON (AP) — An explosion at the finish line of the Boston Marathon Monday killed three people and injured dozens more. The FBI took charge of the investigation into the bombings, serving a warrant late Monday on an apartment in the suburban Boston town of Revere and appealing for any video, audio and still images taken by marathon spectators. The president was careful not to use the words "terrorism" or "terrorist attack" in his remarks, but a White House official, speaking on condition of anonymity because the investigation was still unfolding, said the attack was being treated as an act of terrorism. The FBI, U.S.