To pick up the people, don't run over them. You have to pick up them from the left side. Carefully go nearer the trees, there can be ambushes. Destroy them by means of a machine gun. Trees can be terminated from the regular weapons.
Having picked up the corresponding artifact, you get additional machine guns which allow terminate the stones. The shield which can be found on a game field will protect from enemy bullets.
Watch allows slowing down game speed.
Pick up artifacts to be more effective in your mission.