But McVeigh had another reason–a tactical reason-for taking his time. He did not want to get there too early, before the Alfred P. Murrah Building filled up with people. He wanted his body count….

The nubs of the two fuses he had installed the day before were sticking into the cab of the truck, just behind his left shoulder. McVeigh planned to light the two fuses, park the truck in the small parking area in front of the Murrah Building, and walk away. “If I needed to, I was ready to stay in the truck and protect it with gunfire until the bomb blew up,” McVeigh says….

He approached the building carefully. As his eyes fell upon it, the enormity of what he was about to do hit Timothy McVeigh as if for the first time.

Just as quickly, he pushed the thought aside.

McVeigh finally spotted the location he had chosen for the bomb-a drop-off point, several car lengths long, cut into the sidewalk on the north side of the structure. Not one car was pulled up there when he arrived, and when he realized that fact, McVeigh breathed a sigh of relief. If the drop-off spots had been filled with cars, he’d decided, he would drive onto the sidewalk and crash his truck into the building. That would not be necessary now.

As calmly as any delivery-truck driver making a routine drop-off, McVeigh parked right below the tinted windows of the America’s Kids Day Care Center on the second floor.

McVeigh looked over his creation one last time. The fuses were still burning, the shorter of the two nearly complete. The vehicle was parked exactly where he wanted it, its back end facing the building.

In the next half-minute, perhaps a dozen people saw McVeigh walking away from the Murrah Building. He was wearing a nondescript blue windbreaker over his Abe Lincoln T-shirt, with a black baseball cap, army boots, and faded black jeans.

Looking straight ahead, McVeigh walked at deliberate speed toward the nearby YMCA building, across NW 5th at the intersection of Robinson Avenue.

He never looked back.

From his earlier visits to downtown Oklahoma City, McVeigh knew he could make it behind the YMCA building in plenty of time to avoid the blast, even walking at normal speed.

As he crossed NW 6th Street, a block from the Murrah Building, he noticed a police car parked on the side of the street. Looking out the corner of his eye, McVeigh couldn’t tell if there was an officer inside the car, and he wasn’t about to stop for a closer look. He wondered whether the cop would be looking right at him when the moment came.

He kept walking.

McVeigh counted off the seconds to himself as he walked north into an alley off NW 6th Street. He was now about 150 yards from ground zero, the spot where he had left his truck. Now, with the police car out of view, McVeigh broke into a jog for the first time.

That bomb should have blown by now, he thought. For an instant he wondered if something might have gone wrong.

Oh man, am I going to have to walk back there and shoot that damn truck?

Then he heard the roar.

An observer watching the scene from a helicopter would have seen many of the people of Oklahoma City rushing toward their crippled federal office building. They would have seen drivers abandoning their cars on the road and running toward the blast scene to provide what help they could. They would have seen the flashing emergency lights on dozens of police cars, fire trucks, and ambulances, all heading toward the rising dust and smoke.

And if they looked closely, they would have noticed an old yellow sedan heading slowly in the other direction. After delivering his ghastly wake-up call to the American government, McVeigh was cruising out of town.

He did not go back and look at what his bomb had done to the Murrah Building. The sound of the explosion told him all he needed to know. With a noise like that, he figured, the whole building must have gone down.

He was certain that many had died, and he had no regrets. In fact, he could feel the anxiety leaving his body.

It’s over, he thought.

For more of NEWSWEEK’S exclusive excerpt from “American Terrorist,” pick up the April 9 issue, on newsstands April 2.