>> there was a different kind of bullet that has a circular disk at its base which can then become detached upon impact with the skull. >> the presence of the circular disk rules out any doubt this -- >> orr found another piece of evidence that points to a second shooter, a bone fracture in the president's back. dr. wect who had never considered a bone fracture agrees. >> you can see a clear defect there at the level of the first thoracic vertebrae. >> orr says after the bullet hit kennedy's back it hit bone and traveled upwards. the warren commission -- the panel's measurements were wrong. instead he used the hsca's dimensions, which placed the wound about four inches lower. >> the only thing that's going to cause it to be defect tiff would be something firm and here that means bone.