How can I find a person who broke into someone's facebook account

[adrielalves889]

So two days ago, someone broke into my sister's boyfriend's account and asked her to transfer a large sum of money. I would like to know if there is any way to find out who did it. I exclude the police and the bank because they have already been notified of the incident. If anyone have any advices/ideas, I would be grateful. I also leave my discord if necessary.
Discord: ???#0998