How did marials disappearance change salva

Marial is a young boy, the same age as Salva. The two meet during the march towards Ethiopia and they quickly become friends, mainly because they are the only children in the group. The try to maintain their optimism during the trip but unfortunately, Marial disappears suddenly during one night. The rest of the members in the camp theorize that the young boy was most likely killed by a lion. Salva is very sad and fears that death is an imminent threat.