Has he been diagnosed with anything previous to this?

In my state (Maryland), if you sign yourself in you should expect to be in there at least 3 days for observation & treatment. After the 3rd day, if you want to go, they let you out if you are not a threat, etc, etc..so hopefully he will be in there a few days. They might adjust his meds (if he's taking them) too. Keep in mind the meds take a few weeks to get into the system, usually, so there will be a rough period regardless.

Remember that his paranoia is not his fault, it's his illness. Definitely contact NAMI and pass the info along to his family. I wish I had done it years ago! THey are a great support. They can help with support groups for him, you and his family and can give advice on what to do now and how to be prepared should this happen again.

Good luck to you. Keep your thoughts positive and make sure you stay sane while helping your friend.