Bumping...
Saw on an article that the female "detective" on the ID Disappeared Episode is not a detective at all...
http://www.huffingtonpost.com/2014/03/04/brian-barton-missing_n_4899240.html
Deyo was a "police support officer" and not a sworn law enforcement officer. The above article says an actual Federal Way detective seems to think that there was not foul play in Brian's disappearance. He said the bent screen door was a common feature on apartments in that complex. I think the Deyo "support officer" was given way too much of a role in the Disappeared episode.
In my opinion, Brian Barton had a mental break. He could have bipolar or schizophrenia as others have mentioned on this thread. His anxiety, abruptly quitting the band, mention of the angel coming for him...all of these behaviors point to a possible mental disorder. Schizophrenia could definitely be a cause as well as a bipolar manic episode. I think it's likely he took off on his own volition while confused. I strongly feel that he was homeless as others have mentioned. He could have gone back to his native California. I was born in LA and the homeless population in southern California is staggering and the homeless community is resilient, living on beaches and performing for money. There are enough outreach organizations such as soup kitchens etc for homeless people, at least in California. I saw the same homeless people in relatively good condition (for living on the street) for years. In places like Venice Beach, a lot of them will perform for money, including musically. I think this is a strong possibility for Brian Barton.
Contrary to what Brian's former girlfriend said on Disappeared, I don't think a bottle of Tylenol PM that Brian took indicates he was trying to commit suicide. You would have to ingest a ton of it (it's just Benadryl with Tylenol). Unless he had a large bottle of it that was full, it would seem he took it with him to help him sleep.
On a side note, I don't trust his former girlfriend at all. She came across as disingenuous on the Disappeared episode. I think she is hiding something, but I think it is most likely something like drug use, infidelity, etc.
Thinking of Brian.