I'm not sure what set him off, but I hate to see someone leave the forum upset.
DFF
Then again, as a moderator, I hate speculating as to what caused a forum member to depart. If it's something concrete we can address, we'll address it. If the man is just tired of this place, that's different.
I used to be active in a lot of forums but as I lost interest I just quit posting. No big goodbyes, just faded away.
Some forums will clean up inactive members after a time, but I normally don't delete my own profiles just in case something strikes my interest again. I would recommend that course of action in this case also.