Four Blind Mice by James Patterson. 
With his resignation from the Washington Police interrupted by a case involving a friend who has been framed for murder, Alex Cross and partner John Sampson journey deep across military lines to confront the most brutal killer of their careers.  this latest thriller from perennial bestselling author James Patterson, Washington cop Alex Cross gets involved in his partner's effort to save the life of an old Army buddy who's facing execution for a horrendous and inexplicable murder spree in North Carolina. The Army's evidence against Sergeant Ellis Cooper, a decorated Vietnam vet, is overwhelming, which isn't surprising since it's all been planted by a quartet of killers whose reason for framing the hero isn't revealed until long after they are.