Hearsay will not hold up in court. He may have been exaggerating. The victim would have to be the one to pursue it.
Actually just the opposite. Go to the police department in the jurisdiction where this took place and immediately report this guy. The girl he spoke of is probably not the only victim. In some places, like where I live, it is a crime not to report such an offense.
When a criminal confesses to you something it is not hearsay.