What did Edgar Quisenberry do at the chapter's end? Why?

At the end of Chapter Five, a devastated and hopeless Edgar Quisenberry took his own life.

He found the old, nickel-plated revolver, purchased by his father many years before, in the top drawer of his bureau. Edgar had never fired it. The bullets were green with mold and the ham mer rusted. He put it to his temple, wondering whether it would work. It did.