First of all, make sure that if you repay a debt on behalf of another person, a loan-lending relationship is formed between you and that person, which falls within the civil category.

This person's failure to repay the money is a

civil dispute

subject to the jurisdiction of the court.

If you go to the police and call the police, I’d be surprised if they ignore you. Go to the court yourself and don't say you don't know this person.