. >> reporter: special agent scott lott with the tennessee bureau of investigation takes "20/20" inside the crime scene. >> this is the bedroom where billy was found. >> single shot? >> single shot in the face. >> reporter: billy payne's throat had also been slashed as he lay in bed. down the hall, in the nursery, billie jean had been cradling their baby in her arms when she died. >> that's how they find her, still holding her 7-month child. >> reporter: so it didn't take to this room to shoot? >> no. >> it takes a cold-blooded person to shoot someone holding >> reporter: miraculously, the 7-month-old survived without a scratch. killer had left virtually no clues. were you able to glean very much forensic evidence from this scene? far as physical evidence goes. >> reporter: so no prints, no shell casings, no dna left behind. >> not that we found. no, sir. >> reporter: would that lead you to believe that whoever did this killing had some training? >> it looked like a hit. >> reporter: like a contract hit? >> right. >> reporter: but who in the so-called "friendly hometown" of mountain cit