I think if you go to the police and tell them what you know and how you know it and who(elders and the org) has more information, then you have done your duty.
If you know where he is now, you could go to the elders, state what you know and ask them how they are protecting the children in light of the WTs enlightened response to protecting children these days.
If you want to cause problems, go to old congregations (do the elder confrontation as appropriate) and nose around and if you know of victims (after the WTs first knowlege of him), then encourage them to go to police at minimum. Seeking redress in criminal courts and civil (whether against the perp, the elders or the org, I don't know, that's for an attorney to determine).
If you have a heart for those victims then you can speak up for them until they can, but I think a police report of what you have heard (if it is reliable) along with the fact that you KNOW of others who would have heard the accusations (elders) might be effective. Its not just about the victims he has already harmed, its about protecting the children he has not yet had a chance to harm.