Hi Jothar: You think your Rov was not sure of his answer the first time you spoke to him? You have to be careful in these matters, which it seems you are doing by asking again. I hope you are not jumping the gun on something.
Do you “suspect” something is going on? Or, the fact is something is going on? If something is going on, and you know for sure, and you really know for sure, the answer is clear. Please help the victim.
You are involved at this point and I suggest you possibly go down and talk to a police officer for recommendation on how to handle this professionally. Dont mention names; dont sign anything. See how they approach it. And do it soon.
Hatzlacha!