I only know of a few suicides IRL, and most of them had obvious reasons (money, health, love). But there wa one where no one knew why.
It is very disturbing.
I had the impression a while back (on my first re-read) that, as a baptist sneaking bourbon with his daughter, there were probably other times he snuck it as well, and that he was a closet alcoholic. He made a (probably drunken) decision to save his family from himself. That was just my take, based on what little info there was.
But it also may explain Faye's attraction to liquor as well, since alcoholism, whether genetically transmitted or not, can easily be passed on to the next generation...