A gas chamber

Neither boy knows where this march will lead. However, they are soon crowded into a gas chamber, which Bruno assumes is a place to keep them dry from the rain until it stops. 
 Bruno's family spent several months at their home trying to find Bruno, before his mother and Gretel return to Berlin, only to discover he is not there as they had expected. A year after, his father returns to the spot that the soldiers found Bruno's clothes and discovers that the fence was not properly attached at the base and can form a gap big enough for a boy of Bruno's size to fit through. Using this information, his father eventually pieces together that they gassed Bruno to death.

This part make me cry, because it was something unexpected. I was too sad because Bruno´s family was looking for Bruno and Bruno was already death in the gas chamber.