Firstly, I am glad your kids are not crazy, whatever our definition of crazy is.  But, no matter how good parents we are, there comes a time when our children are not in our control and are making choices on their own.  

Many things happen in peoples lives that are out of our control as parents.  

Things happen, not involving substances, that are out of our control.  For example:  "The first episodes of schizophrenia, bipolar disorder and major depressive disorder tend to appear in the late teens and early 20s"  (I'll put a link to the article below, it is interesting and informative)

I have not ready anything yet that said this individual had tried to hurt anyone.  I've read possible suicide intention.   Trying to get help for mental issues in this state is hard, this person may have been at their wits end trying to get help.

http://www.nbcdfw.com/news/health/The_Real_World__Recognizing_Mental_Illness_in_Young_Adults.html