Around two years ago in Dhaka, I was at a class and I overheard two guys talking.

One was saying to the other that:

two, three nights ago he had sex with his girlfriend in a friend's car. He also mentioned that his girlfriend was high. He even mentioned that later on his girlfriend told what he did to her, to her mother. He even mentioned that there was the driver of the car, whom he gave Tk50 to keep his mouth shut.

I do not know much details about the case. I know the offender's name, school and friends.

Also, note that he mentioned that some of his friends including the owner of the car knew about this as well.

If I want to remain anonymous and still bring this person to justice what should I do?