He needs an immigration lawyer, right away. If he has an ICE hold and no pending charges, he needs to deal with ICE.
This response does not create an attorney client relationship and is offered for informational purposes only. Only a lawyer fully versed on the facts and circumstances of your case can properly advise you on the case. I am licensed to practice in Minnesota, not every state. You should always consult with an attorney licensed in your area on how best to proceed.
It sounds as if he has an ICE detainer. Until the immigration issue is resolved, he will remain in custody. Hire an immigration attorney ASAP.