FBI, CIA, NYPD, or MP?

I'm a sophomore in highschool and I know I've got awhile to think but, what job would be best suited for me, I really just want to help people actively so desk work and guarding evidence isn't really something I want to do all day. I could care less about pay, that doesn't really matter to me as long as I'm helping people. In fact if you want to recommend another police force go ahead. I want to stop drug trafficking/dealing, protect children from domestic abuse, that's a big one. Stop kidnappers. The big stuff. Ive considered st. Luis Pd. But can anybody tell me what you do if your a CIA/FBI special agent or an MP? Thanks!