My ex sent x-rated pic of himself to my daughter!!

First of all, I used to post on here and found great support several years ago. This forum and counseling saved my sanity. I was married 30 years to my narc and didn't realize the depth of his perversity until the last 4 years. I now have been divorced 6 months and moved across country and had been able to keep no contact. I have been moving forward and doing better. Then yesterday my youngest sent me a private FB message as follows: WARNING DO NOT READ if other young eyes can see this:

"And.. something happened last night that really freaked me out. It's been bugging me all day and I didn't know whether or not I should tell you, but around 8 this morning I got a text message and it said it was from dad, so i opened it and it was a picture of him jacking off. F***ING disgusting and I am completely scarred. I figured maybe he meant to send it to "Myra" and maybe her name was next to mine on his list of contacts? I dont know, but either way I'm totally grossed out and traumatized. I don't know what to do, please don't tell anyone. I just want to keep this between me and you.
Anyway, I just needed to get that off my chest. :( I love you, hope I didnt upset you too much by telling you. I work all day tomorrow but I'll try to give you a call"

OMGGGG all the wounds are open again what a FREAK. He was into pornography and I think more than likely he meant to send it to someone else but STILLL EWWWWW. I haven't been able to contact her yet, probably today,but I think it is clear she feels shame from her post (don't tell anyone) and he is a master at piling on guilt and shame. Any suggestions are welcome on how to best help my daughter!! My thought is if she doesn't want to speak with him, to just return the text back to him (so he knows what he did) with a short message. My other daughter has already blocked all contact with her father, but this child was gone when a lot of the really bad stuff happened and didn't see it, and you all know how good these narcs are at covering up and blaming and making themselves look good. I am just heartsick.