Complex sentence: As the Nationalists began to march, the police, empowered by the North American police chief, and encouraged by the governor, opened fire with impunity on cadets and bystanders alike for over 15 minutes from four different positions-killing men, women and children.
Split into simpler sentences: As the Nationalists began marching the police-empowered by the North American police chief and encouraged by the governor-opened fire on cadets and bystanders alike. Firing with impunity for over 15 minutes from four different positions, they killed men, women and children.