Despite all his efforts to keep his son safe, Guido unwittingly tells his son to go to the gas chamber:
Giosué: Daddy, I cannot find any of the other kids, and a lady came telling me to take a shower.
Guido: That's a good idea. You go take a shower.
Giosué: No!
Guido: Go take a shower!
Giosué: No!
Given that we only see Giosué when the camp is liberated, all the other inmates we saw during the course of the film were probably killed when the camp was liquidated.