The Guilty by David Baldacci

The fourth novel in the Will Robie series – Robie is sent to assassinate a potential leader who wants war with America.  But when he pulls the trigger, he finds a little girl had run into the room right behind the target and his bullet has killed both.  On his next mission he hesitates because he sees a little boy jump into the target’s arms.  Only it didn’t happen and Robie did not pull the trigger.

He’s sent to Cantrell, Mississippi where he grew-up because his estranged father has been accused of murder.  When he arrives, he finds out that his father remarried and has a very young, autistic son.  Robie has a half-brother.  He soon finds that there are very questionable things going on in the town and his partner, Jessica Reel has to intervene and come to his rescue.