I understand so well, the wonderful memories of our children, how sweet - kind - considerate they used to be. We absolutely have to put that on a shelf and know who they are this very moment. As Copa said he overdosed in your own home, nothing can save him but himself. Nothing you did in the past or any help at the moment will magically bring him back to the boy you remember.
Thank you for your kind words towards my daughter, we are learning through trial and error. I just hope to spare someone the pain of 10 years in like me. 
Just had to add that after my daughter just up and left us, better living out of my car than with you 2!, I went into a deep depression, cried all day/night, nothing but thoughts of her every waking moment. I thought of her committing suicide/worst case scenarios as she is prone to attempt killing herself due to her mental conditions. It’s a rough road in the beginning, the very worst! It does get a bit easier I will say as time goes on.
