You haven't asked a question this time. If he gets an immigration hold, he'll need an immigration to help him out with those proceedings.
If he does get charges filed against him, he'll need both a good criminal defense attorney AND an immigration lawyer
Please pardon any typos - posted via mobile device.
The above answer is for general information only and is based on the information you posted. Every case is fact dependent, so to get a thorough analysis of your situation, you will need to consult face to face with an attorney licensed to practice in the jurisdiction where the incident took place. Do not conclusively rely on any information posted online when deciding what to do about your case.
Consult and retain an experienced criminal defense lawyer ASAP. Early representation many times will make a big difference in protecting the accused. Regardless, the potential accused should not under any circumstances give a statement to the police. PERIOD. Trying to "talk your way out of it" is not advised. Prior background will be another negative for the person involved in your question. Be aware and beware. The 5th amendment right against self-incrimination is a critical right that should be asserted in almost every case. Consult an experienced local criminal defense lawyer ASAP.
Please do NOT use this answer/response to say or do anything regarding your situation. This answer/response is based on the information provided in the question asked and requires a much more complete context than is available in this public forum. BEFORE you say or do anything consult with an experienced Federal and/or state criminal defense attorney in your jurisdiction who will listen to you and your concerns.