During one hanging Elie and the other prisoners cried. What made this hanging different from others?

In Chapter 4, Elie witnesses the horrific, tragic execution of a young pipel, who is hanged in front of the prisoners. What makes the pipel's execution particularly difficult to watch is the way he suffers during the hanging and the fact that he resembles an innocent angel. After the block leader is arrested and executed for possessing a small arsenal in the Buna camp, the SS officers arrest the small pipel, who worked for the block leader and is describes as a "sad-eyed angel." As the young boy stands on the gallows, one of the prisoners asks, "Where is merciful God, where is He?" (Wiesel, 89). The two prisoners and the pipel are then hanged in front of the crowd of Jewish prisoners.
Tragically, the pipel is too light and does not die immediately when he is dropped from the platform. The young boy simply swings from the rope, lingering between life and death for a half an hour. The prisoners are both disgusted and deeply saddened after witnessing the awful execution of the young pipel. They not only shed tears but begin questioning God as the young boy suffers in his death.

Eliezer, like all the other prisoners, is forced to witness many atrocities in the camp, including many hangings. But one in particular has a profound effect upon him. One day, a young assistant of a Kapo is arrested along with the Kapo and two other prisoners for blowing up the Buna power station. All the suspects are brutally tortured by their Nazi captors, but they refuse to confess their guilt or implicate others.
Inevitably, they are all subsequently hanged. And it is the hanging of the young boy, the Kapo's assistant, that sticks in Eliezer's memory. There is something about his face that is so fresh-faced and innocent. The other prisoners feel the same way. It seems that, even by Nazi standards, this represents a new low in cruelty and degradation.
A man in the crowd cries out, "Where is God now?" As Eliezer walks past the boy, dying a slow and painful death on the end of a rope, his belief in God finally ebbs away. Earlier, he stopped praying to God because he no longer believed that he was just. Now, the brutal execution of an innocent child has convinced him that God isn't simply unjust; he doesn't even exist.