Have people asked him to stop?
It's important that should happen, and it be done in public.
That way when it happens again, you have something to report.
He can't get away with the bull shit of "Nobody told me." and "I was just being friendly."
It has to be made clear to him that he is making the person uncomfortable, even if it's obvious to everyone with frelling eyes, you can't assume he has a brain or cares.
Since you can't count on the ETLs to handle this, you'll have to watch the person ask him to stop, record his response and then when he does it again, report it to the hotline.