The fix / David Baldacci.

Walter Dabney is a family man. A loving husband and the father of four grown daughters, he's built a life many would be proud of. But then the unthinkable happens. Standing outside the FBI Headquarters in Washington, DC, Dabney shoots school teacher Anne Berkshire in cold blood before turning the gun on himself. One of the many witnesses is Amos Decker; a man who forgets nothing and sees what most miss. Baffled by what appears to be a seemingly senseless and random killing, Decker is thrust into the investigation to determine what drove this family man to pull the trigger. As part of an FBI special task force, Decker and the team delve into the lives of Dabney and Berkshire to find a connection that doesn't seem to exist. What they do find are secrets that stretch back a lifetime and reveal a current plot of impending destruction that will send the world reeling, placing Decker and his team squarely in the crosshairs.