On April 19, 1995, 168 people were killed when a 4,800-pound bomb detonated at the north entrance of the Alfred P. Murrah Federal Building in downtown Oklahoma City. The explosion wounded nearly 800 more, collapsed a third of the building and damaged hundreds of other buildings in the area. It remains the deadliest single act of domestic terrorism in American history. National Geographic's Emmy-winning series "One Day in America" marks the 30th anniversary of this tragedy with a three-part