Desperate Measures by David Morrell

Desperate Measures by David Morrell is an old book (1992) about a journalist who has lost his edge due to depression from the death of his son.  He postpones his plans for suicide to do a favor for his friend and editor.  He must write an obituary for a man who is still alive.  The assignment becomes dangerous when the subject is murdered and the journalist becomes a suspect.  As assassins try to kill him, he realizes that he wants to live.