Hi again Neglected:
If he is only on day 4 and if he is truly not taking anything, get ready for some pretty hefty withdrawals. You can read a lot about what those are on some of the threads. Opiate withdrawal usually causes gastrointestinal distress (stomach cramps, nausea, vomiting, diarrhea, etc.), hot/cold chills, restless legs/restless body, severe insomnia, racing crazy thoughts, body aches big time. Just for starters. Most people in withdrawal get to feeling pretty bad, and if he is doing this without help, you should figure out ahead of time where you will take him if he starts to freak out because he feels so sick. He is unlikely to get through this with a smile.
I still think calling your local drug hotline would be a good resource for you, and you can find out where to get help for him. He may need inpatient rehab.