(((gismo)))
Sounds like a very uncomfortable and scary experience to me!
It's hard not to become emotional after witnessing an event like this. Especially when you know one of the people involved well. I am sure that the event was very distressing to you and your son-in-law.
The time that sexual predators serve disgusts me, it's insulting IMO! Especially because the chances of them re-offending the same laws are pretty significant. Scares the bejeezers out of me!

Making the neighborhood aware of this man would certainly help. I, too, advise you not to approach this man. I wouldn't want to trigger him into poor behavior.
Please be careful ~ gentle hugs sent to you and your family.