After reading a bit too much about this for the past couple of days, I am leaning towards either a hookup gone bad or an accident in the dark park, or both. I think the chances that BB went to the park for a hookup are very high, but I don't think we have evidence as to how that hookup turned...
There was a report somewhere (another website I think) from an unverified classmate that he had been on leave for six months. I think that's the entire source of that claim.