I do not understand: the FBI makes a decision but if you want to compel the authorities to do something, should you not have to denounce a crime? An investigat

I do not understand: the FBI makes a decision but if you want to compel the authorities to do something, should you not have to denounce a crime? An investigation is not the pursuing of a criminal (albeit it may end there). It is the role of the FBI to decide when to pursue. I am not defending the FBI, just trying to understand. I know denouncing the abuse formally is practically impossible without help. So, I am not trying to criticize the victims here.