Priests are not allowed to reveal secrets of the confessional. But he would certainly have counseled them on what to do, had they confessed honestly to him (which I doubt that they did).
I think he was a simple village priest and they took advantage of him. Did they kill their daughter? I don’t know, but they were real publicity hounds, and I think they definitely exploited this priest.
I don’t believe he can even comment on what was NOT confessed or any communications within the Sacrament of Reconciliation, so he is probably truly over his head with the public attention.