It took eight seconds on the morning of April 19, 1995, for Americans to be jolted out of complacency concerning terrorists within their borders. A bomb exploded in the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma. The nine-story building was completely destroyed in that short time, with the floors imploding and toppling down upon each other. When the 27-foot-high pile of glass, steel, and concrete had settled, the process of identifying 168 corpses began; 19 of them were children.

At first, a stunned public assumed the bombing was the work of international terrorists. But less than two hours later, Oklahoma state trooper Charlie Hanger arrested American Timothy James McVeigh on charges of driving without license tags and carrying a semiautomatic pistol loaded with "cop killer" bullets, which can penetrate bulletproof vests. Hanger did not realize at the time that he had found a home-grown terrorist. On June 2, 1997, McVeigh was found...