Lil, you seem to be struggling about how this could happen to an upstanding family like yours. It can happen in any family and does. I have been a high school math teacher for over thirty years and my husband was in the software business for over thirty years and is now teaching high school, also. Many of us on the board are professionals with college degrees and have been good role models for our children but, for whatever reason, they took a very different path. Many of us also have a easy child so it obviously can't be just parenting.
Personally, I believe my difficult child was hardwired differently. In her case, mental illness played a huge role in her substance abuse and the dysfunctional life she was leading. She is doing better now. but I still see lapses in judgment due to her mental health issues.
All of us reach our breaking points at different places. This is all still new to you and you aren't ready to give up on him yet which is fine. Hopefully your son will listen. He is still young so as a member used to say, "he's not done cooking yet."
~Kathy