Earlier quoted context omitted.
Why didn't you contact the police first?
Yeah honestly if I saw something like that I would have saved an offline copy on a USB stick and handed it to police for investigation. The problem that it even happens is much greater than the problem of online distribution, and deleting it and pretending it didn't happen isn't a satisfactory response.
I have done work for lawyers in exactly this scenario. Be very very careful.
You do not want to have to explain to explain the provenance of such a file without having someone to back you up.