Lots of good responses here. That’d be a really scary find, OP, and I’m sorry you’re dealing with that. :(

As much as I also long for justice, I also totally understand the inclination towards just nuking and paving the whole thing and moving on. Some factors that occurred to me:

Those posting it might be outside your nation’s jurisdiction.

They might just be bots.

The above, plus they might be using “zombie” machines to bounce this material around unguarded servers wherever they can. It could be very difficult to ascertain who is behind this.

I agree with others that you should only move forward under the guidance of a good lawyer, because you don’t want to be the most convenient potential suspect they have access to.