what is or who is the inciting force in this story?

Salva is in his classroom studying. Suddenly, Salva hears the sound of gunfire from outside. The teacher shouts for everyone to get down as the gunfire continues. All Salva knows is that rebels from the south, where he lives, are fighting against the government in the north. Salva is forced to flee into the forest: his childhood will never be the same again.