Salva has been left behind he has no one to look after him. They left him behind because he was just a boy he would slow everyone down and be another stomach to feed. He feels betrayed.
Salva's Uncle past away none of the group will feed him. He has to beg for scraps. He has to mature and care for himself. His uncle said only a few people escaped Salva's village and his family probably died. Witch means he has to mature and take care of himself.
Throughout the passage Salva developed into a leader. He had to lead fifteen hundred boys to a refugee camp in Kenya. Along the way Salva gave jobs like collecting wood for fires, guarding the group as the group slept, and scavenging for food. Sometimes Salva had to coax people if they denied to work.