Young couple goes on van tour of US, boy comes back with van - no girl

I have nothing to base this on, but my hunch is he offed himself. I have to think he's realized what he's done and to someone I think he probably cared about. Just have a hunch he might not be able to live with what he did.
Here's the thing, though, how long did it take him to come to that realization? He had the whole ride home to think about it. Then he had the family camping trip to think about it. So after all that, THEN he can't live with himself? Or is it that he finally figured out after 2 weeks, Hey, maybe somebody might come looking for me, I guess I'll kill myself. That plus the parents not particularly freaking out about their 23-year old son's possible death makes me press X to doubt.