In The Boy in the Striped Pajamas, what actually happened to the boys at the end? Did Bruno die?

The Boy in the Striped
Pajamas by John Boyne is historical in nature but is a fictional story which
reminds readers of the disaster and tragedy of Nazi occupation. Bruno must move because
of his father's profession which, in itself, is nothing unusual but he would thrive in a
situation where he is allowed to develop and mature at his own pace. He is forbidden
from exploring and making new friends is impossible. It is significant that it is
Bruno's father's behavior which, in fact, directs Bruno's actions. The boys are thrust
together by circumstance and this story indicates the tragedy and futility of war and
also highlights the similarities between these innocent children, regardless of which
side they are supposedly on. Bruno and Shmuel come from worlds so far removed from each
other that an event of this nature should not be possible. However, John Boyne
skillfully points out through Bruno's character, there are more things that unite Bruno
and Shmuel than there are things that separate
them. 

Bruno's father, a powerful Nazi Commandant, has
convinced himself that "Those people...well, they're not people at all..." (chapter 5).
This is ironic considering that Shmuel is Bruno's only friend with whom, if his father
is correct, Bruno has "nothing in common." However, Bruno and Shmuel share an
unexplained bond, which starts with them sharing a birthday. After a year of meeting and
chatting, Bruno is due to return to Berlin and so he and Shmuel discuss the possibility
of him going to Shmuel's side of the fence. Bruno's hair is short, having been shaved to
avoid lice and, as Shmuel points out, he is a little "fatter," but, otherwise, in a
"pair of striped pajamas" he would look essentially the same as Shmuel and they can go
on a "final adventure" in the camp. Bruno is excited at the prospect of "exploring" and
Shmuel is anxious that Bruno will help him look for "Papa," who has apparently gone
missing. The boys sense that this will seal their friendship and is a good way to say
"goodbye" (chapter 18). The reader senses that this foreshadows more sinister events to
follow.  

Bruno is shocked that he has to walk barefoot and
that he sees mostly sad faces; the camp is nothing like he expected. He and Shmuel find
no trace or "evidence" of Shmuel's papa either so Bruno is about to make his way back to
the fence and go home when a whistle sounds and the boys find themselves in the middle
of a crowd. They are ushered into an "airtight" room and Bruno tells Shmuel he is his
best friend and holds his hand but has no idea whether Shmuel replies because "at that
moment, there was a loud gasp from all the marchers..." and Bruno can hear nothing. He
wonders about the darkness but in his innocence presumes it is related to the fact that
it is raining outside. After that, "Nothing more was ever heard of Bruno..." The reader
knows what has happened and takes solace in the fact that Bruno is not afraid in his
last moments and that Shmuel has his friend with him. The boys have evidently been
gassed.