Fraud induced me to invest with fake broker

At first, we videoed chat with each other and then we chatted via ohone. He said he was a mainland migrant and now lived in Singapore. He claimed himelf to be rich. And he studied in Peking University and was good at math. He learned investment. So he attracted me to invest with him. I profited. But I can't get the money without adding more money. This is a scam. He told me that he withdrew a lot of times and then I asked him to give me his screenshots about his withdrawal. But he refused. I've lost $50，000. He pretended to help me but made my account become abnormal account and I had to deposit funds. He said all his family could get the withdrawal, and I am an exception.