Being Accused Of Fraud

I came to Delhi for my higher studies from south India. More than a year ago, one of my classmates asked if I can give my account details so that his brother can transfer some money as he was having some issues directly transferring to his account. It seemed a genuine issue and I had no reason to suspect so I got the money and transferred all to my classmate's account. It has been almost a week, I started receiving unknown calls that I was party to fraud as this money was transferred in lieu of clearing the competition exam with impersonation. Both parties, my classmate's brother and the sender of the money are apparently lawyers. I do not know what to do, the other guy keeps calling threatening police action. But my classmate is saying like If you respond to him, you will be involved. And this party can only threaten because he did it for illegal activity. Kindly suggest what should be my next course of action.