In his book Vanishing Grace, Philip Yancey shares a story about a World War II veteran, currently serving as a pastor, who had participated in the liberation of the Dachau concentration camp. At the end of the war, as the U.S. soldiers marched through the gates of Dachau, nothing could prepare them for what they found in the boxcars within the camp. The man said,

A buddy and I were assigned to one boxcar. Inside were human bodies, stacked in neat rows, exactly like firewood. Most were corpses, but a few still had a faint pulse. The Germans, ever meticulous, had planned out the rows—alternating the heads and feet, and accommodating different sizes and shapes of bodies. Our job was like moving furniture. We would pick up each body—so light!—and carry it to a designated area. I spent two hours in the boxcar, two hours that for me included every known emotion: rage, pity, shame, revulsion—every negative emotion, I should say. They came in waves, all but the rage. It stayed, fueling our work.

Then a fellow soldier named Chuck agreed to escort twelve SS officers in charge of Dachau to an interrogation center nearby … A few minutes later the crew working in the boxcar heard bursts of a machine gun. Soon Chuck came strolling out, smoke still curling from the tip of his weapon. "They all tried to run away," he said with a leer.

When Yancey asked if anyone reported what Chuck did or took disciplinary action, the pastor said,

No, and that's what got to me. It was on that day that I felt called by God to become a pastor. First, there was the horror of the corpses in the boxcar. I could not absorb such a scene. I did not even know such Absolute Evil existed. But when I saw it, I knew beyond doubt that I must spend my life serving whatever opposed such Evil—serving God. Then came the incident with Chuck. I had a nauseating fear that the captain might call on me to escort the next group of SS guards, and an even more dread fear that if he did, I might do the same as Chuck. The beast that was within those guards was also within me.