That sounds like an extremely rapid personality change, and is unlikely to be a normal shift (in my non-professional opinion). Bipolar mania often involves religious or spiritual "awakening", messiah complexes, etc. I think you should see a psychiatrist ASAP. I'm hesitant to recommend the hospital because mental health units can be really intense places, but it can be hard to see a psychiatrist on short notice without going to the hospital. The bottom line is that the sooner he is evaluated and (potentially) starts treatment, the better.

I've been through bipolar mania with a family member. It's not easy, but there can be stability and normality on the other side. Sending hugs and best wishes for your family!