Will he be released from immigration?

My cousin was arrested and sentenced for fraud. His sentencing was 160 days in prison and he payed a restitution of $ 30,000 and got out with time served. He came to america legally...and has been here for 4 years. this is his first crime.. after his release and case closed immigration scooped him up and we thought he would be released but they took him into their custody and now he is sitting there. what will happen to him? will they put a bail? how come he wasnt released after paying the 30,000. He sat less than a year for his crime. Is he deportable? can he fight this case and stay?