This. Do not make this person feel as if you did the one thing they precisely didn't want you to do. Doing so means future incidents (of any sort - people don't

This. Do not make this person feel as if you did the one thing they precisely didn't want you to do. Doing so means future incidents (of any sort - people don't like to talk to betrayers) are unlikely to be reported at best. Earlier advice regarding lawyer up, for gods sakes still applies, but you now have a human obligation to the person who reported this in confidence.