Salva was crying because his group left him behind and he had nothing to eat or to drink also he had no body to take care of him but he relied on the lady that he sees on the front porch of the house. Also he felt betrayed
He found his uncle and he was very happy and he felt safer, that he had some one to take care of him so he followed him and his uncle took care of him.
Salva became a leader by how he helped his group of 1500 boys cross the river to get to safety and when they crossed the river the boys would follow him because he is older and can depend on him. Also he got then to refugee camps so they would be safe.