If this is a practical, rather than hypothetical, question, the best advice that we could give would be to see a lawyer. If you think your teenager has done something illegal, get a lawyer. The lawyer will then take care of notifying the relevant parties and manage the accusations.
In most cases, it would be sufficient to notify the police directly. They understand the concept of scams, and many of them have teenagers of their own. Most of the time, they will try to work with you rather than against you. But if you are really worried about it, this is what lawyers do. A lawyer can separate the teenager and the police, so the teenager makes no admissions. But the lawyer can get the necessary information to the police so that neither the teenager nor you is subject to an obstruction of justice charge.
We can help you by pointing to resources or suggesting ways to document what has happened or is happening. Or just point out that something is a scam. But if you are worrying about prosecution, we can't really help you. You can't confide the relevant details to us. There is no asker/answerer confidentiality. Everything is published on the internet with archives. Without those relevant details, how good will our advice be?
Talk to a lawyer. The lawyer can tell you what you can and cannot do. And what you tell the lawyer is privileged. So even if you admit criminality, the lawyer can't then tell anyone. And if you're worried that the lawyer might be restricted by what you've said, you can fire the lawyer and hire another.
The first thing to do when you find yourself in a hole is stop digging. Trying to fix things for your teenager is digging. Go to a lawyer and share your concerns. Maybe some of them are groundless. From what you've shared, you could go to the police. But perhaps there is more that we don't know. If so and you are reluctant to share publicly on the internet, that's sensible. Go to a lawyer and share in private.
If you are indigent and can't afford an attorney, look into Legal Aid. They may be in the phone book. If not, call the local bar association and ask for a referral for free legal advice for someone low income. Try to have a generic description of the problem, e.g. you're worried that someone scammed your teenager into doing something illegal.
And just to say this one more time. As you've described things, it seems like you should be able to just go to the police and the bank and describe the scam. I don't hear anything that they would prosecute. If you've left something out that changes things, then a lawyer is the way to go. Then you can disclose everything to get advice.