I found some sexually explicit photos depicting a four year old girl and an adult both of which I know?

both of which I know personally. This guy should be arrested and I will go to the police but the problem is that the adult was smart enough not to show his face in the photos but I recognize his arm and hand because I've known him for thirty years. I need to make sure this guy goes down this time because he's done this before and gotten away with it. Is their an organization that specializes in this sort of thing that would be better to go to besides the police?