Swift Vengeance - T. Jefferson Parker

Roland Ford is on the trail of a mysterious killer who is beheading CIA drone operators and leaving puzzling clues at each crime scene. His troubled friend Lindsay Rakes is afraid for her own life and the life of her son after a fellow flight crew member is killed in brutal fashion. Even more terrifying is the note the killer left behind: ''Welcome to Caliphornia. This is not the last.'' Ford strikes an uneasy alliance with FBI agent Joan Taucher, who is haunted by what she sees as the Bureau''s failure to catch the 9/11 terrorists. As the killer strikes again, Ford and Taucher dash into the fray - each ready to risk it all to stop the killer.