A difficult one to poke my nose into gypsy mom. It sounds very much like a psychotic event, I had one that lasted from May 2005 and ended in June 2009. I would really need to know what he was or had been taking at the time - legal or otherwise to assess whether it was drug related.
Other than that, my research has taken me to Chromosome 22 - this little DNA bugger is full of imprinted genes - genes that when triggered cause things to happen physically, mentally etc. Most are dormant genes that were part of our ancient survival mechanism _ I believe that the Bi-polar gene is in this region of the DNA. SO, if a dormant (in most western cultures) nomadic gene was triggered; like geese fly south in the winter etc., your son may have suffered such an event. However, mention this to a psych and you may end up being treated yourself. I have done extensive private research (because of my own problem) and I was amazed at what I found. Or, it could be just a dietary trigger; Goggle this (abc steve simpson law of locust )

I hope you find an answer, however let him get involved too don't treat him like an outsider and don't imagine for one moment that professionals will have an answer - its just far too hard for them.

I was in ER one night. This Canadian guy had been there for 48 hours while they did test after test. I poked my nose in and asked what his problem was - it was a respiratory problem - he had flown from Canada to Perth Western Australia (where I live) from winter/fall to summer/spring. Step off the plane and choked with an asthma attack. I asked if it was okay indoors - he seemed alright in the hospital - he said yes. I told him it was pollen this city is full of it - and the so called doctors didn't have a clue and the cost of test and hospitalisation was amazing. Common sense and a good general knowledge can solve most problems.

Take care darling and all the best for wandering boy - Love Jasmine