exit ramp and another about 200 feet away. >> our forensic people were able to tell us that it most likely was an ak 47 type rifle, an assault type rifle. >> knowing that megan had been assaulted with this ak-47, again, is just send chills of agony through my mind. >> investigators also noticed a fresh scrape along the driver's side of the car. it looked as if megan's car had been sideswiped. then investigators got a huge break. they learned that megan's rental car was one of the first to be equipped with an event data recorder. >> the event data recorder is a huge step forward in traffic safety. it's like the black box in an aircraft that gives us a better understanding of how crashes happen. >> the recorder, a small onboard