What does Bruno say and do to show his growing understanding of the inhumanity going on around him including to his friend shmuel

Bruno first recognises the inhumanity going on around him in lessons from other people. The worst of these being Lieutenant Kotler who shoots a stray dog, beats Pavel, and treats him like an ignorant little kid because Kotler knows he hates it. Bruno begins to show his understanding of what is going on around him by asking Gretel about the people he can see out of his window and the big fence. He notices small things too, like how skinny Shmuel, his new friend from the other side of the fence is, and how hungry he always is, although he doesn’t really understand what these things mean until Gretel tells him that the people on the other side of the fence are Jews, and to stay away from them.