Stepdaughter who took nude photos of herself and shared them with an anonymous person is now being blackmailed. How do I handle this?

I don’t really know where to start with this, but I am in desperate need of help in how to support my SO and stepdaughter as we go through this rabbit hole.Am on mobile, advanced apologies for typos and formatting. Also, this is fairly long winded.TLDR; SD took nude photos of self and sent them to someone. Is now being blackmailed for more. Reported to police but don’t know how to help SO & SD thru this. Need help and support.SD= Stepdaughter, pre-teenSO= Significant Other (Her Father)BM= Birth MotherGM= GrandmotherRO= Resource OfficerSunday evening during dinner my SD informed my SO and I very nonchalantly that she had been to the police station that day with her BM and GM. I quickly questioned why she was there and SD said she was reporting some “pedophile” stuff that happened. I inquired further and SD claimed she received instagram messages in the middle of the night that stated they had 500 photos and 20 nude videos of her that they were going to distribute to her friends and family if she did not respond within 4 hours with more photographs. Asked SD if this person did in fact have photos of her and if she has seen them. SD responded that at least one photo they sent to her as proof for blackmail purposes was in fact her, but she had blocked him and could not access the messages of a blocked person. I asked SD how this person got photos of her, and she claimed he hacked an app called LiveMe and gained access to her phone camera. My SO and I kept the conversation pretty short with SD as it was late at night, and I felt we weren’t getting the whole story. We intended to speak to BM & GM the following day to figure out why SO was not involved in this incident and why we are just now finding out about this.Sent SD to bed and told her to call me or text me immediately if this person contacts her again. SD was having major anxiety, shaking, was really embarrassed and worried. Comforted her the best I could, and followed up with her Monday at school. SD said she’s not heard from anyone about anything so she felt she safe. Met up with SO and SD Monday night and everything seemed fine. No issues at all. However we were unable to reach BM & GM to discuss the original instance.Now today, Tuesday. About 3 hours ago I get a text from her:SD: “[myname] I need help”Me: “What’s up?”SD: “The guy is sending my stuff to people”Me: “How did he contact you? Who received it?”SD: “my friend got it”Me: “Tell her not to delete it and keep the message, we need to show this to the cops right away”SD: “I am scared i am freaking out”Me: “are you at school?”SD: “yes”Me: “Okay I’ll be right there”SD: “My friend got them she is texting me”I rushed to the school, tried calling SO but he wasn’t reachable at the time. I met SD in the school office and asked for a private place for us to talk. SD showed me her phone and the texts she was receiving from her friend. It appeared as if the Blackmailer was messaging people SD had followed on Instagram and was saying things like “I have photos of your friend, if you don’t tell her to talk to me I’m sending them out”. Her friend responded with a lot of “no!” and “don’t do that” type stuff. Her friend was then sent a nude, chest up, photo of SD as proof and claimed he had more. Blackmailer said if SD doesn’t send more photos that he will continue to contact her friends/family and send what he does have until she complies.I got up from the room and told SD that I was involving the school resource officer immediately. RO took SD and I into his office and we started to question SD on the entire instance. It was quite clear that SD was not telling us the whole truth, and after about 30 minutes of talking she finally opened up and shared with us that she did in fact take 3 photos of herself and sent them to an anonymous person thru the LiveMe App about 6 months ago. RO contacted the local PD and got the Sex Crimes Devision on the line and informed them of what happened and made a report. RO was given access to all of SD’s social media and we allowed them to speak privately as well since she seemed reserved and not willing to be totally honest with SO and I in the room (SO arrived about 45 minutes into this meeting and was filled in with what was going on). SD was educated on internet safety and why what she did was wrong by RO after the meeting. SD wanted to go home from school, but SO and I decided school was the safest place for her right now. And currently only Family, RO, and this one friend of hers knows what’s going on.HOWEVER-Blackmailer continues to contact her friends and is still sending out her photos.We just left the school about an hour ago and we are both really flustered and not sure how to handle this situation. We aren’t necessarily mad at SD, we are disappointed in her choice to send these photos and the safety risk it brought upon her. She’s grounded, SO is taking away all electronics including her phone. We are more concerned for her safety than anything else at this current moment.What as parents can we do to help SD through this? How can I as a Stepparent support my SO through this time, and also help be there for SD?I understand we all do stupid and dangerous things that we inevitably regret later on. And I’m definitely someone who’s fucked up BAD in her past and had it thrown in my face later.But in this case, I don’t know what to do! I feel I’m in a weird place right now and not sure how to help or be supportive. What can I do? How can we as parents protect our kids?My own daughter, I have access to about 90% of everything she does in her phone, and it’s only usable in WiFi, doesn’t have a phone number. She uses it for TikTok and games. But that’s what we thought SD was doing too.Did we fail SD somehow as parents?Sorry for the long read... my brain is mush and I’m so tired... I just don’t know what to do right now. via /r/Parenting http://bit.ly/2Rn9jZy