On the morning of April 19, 1995, a truck bomb exploded at the Alfred P. Murrah Federal Building in Oklahoma City. It was the deadliest act of domestic terrorism in U.S. history.

The blast was equal to nearly 4000 pounds of TNT. It killed 168 people. Hundreds more were injured.

The federal office building also housed a day care center. The explosives-laden truck was parked directly beneath it.

Of the 21 children there that morning, only 6 survived.

PJ Allen was one of the survivors. He suffered broken bones, severe burns, and damage to his lungs from inhaling debris.

At StoryCorps in Oklahoma City, he spoke with his father, Willie Watson.

Listen to another survivor story here.

Originally aired April 17, 2015 on NPR’s Morning Edition.