How is the scene where Bruno tells Shmuel that he is his best friend an example of dramatic irony?

Dramatic irony is a type of irony in which the characters are unaware of the situation they are in, while the audience is fully aware of what is happening. At the end of the novel The Boy in the Striped Pajamas, Bruno and Shmuel are standing inside of a gas chamber when Bruno tells Shmuel, "You're my best friend, Shmuel...My best friend for life" (Boyne 213). This scene is an example of dramatic irony because both Bruno and Shmuel are unaware that they are standing in a gas chamber about to die. The audience knows that the boys have entered the Auschwitz gas chamber because Boyne writes that the prisoners were unwilling to walk, and they entered a "completely air-tight" building. Bruno implies that he is looking forward to spending more time with Shmuel by calling Shmuel his best friend. Tragically, the audience can predict that both boys will never get the opportunity to play together because of their impending death.