barroso, a 20-year-old college student who lived nearby. her purse was covered in blood. her cell phone was inside. it looked as if she had tried to use her phone to call for help. >> she had gone to a fourth of july party with her best friend and some other young people. i believe in the beach area. >> according to friends, megan left the party alone at 2:45 a.m, a little more than an hour before her car was found. police checked local hospitals, but no one matching megan's description had checked in. >> we didn't know if this person was either dead or alive at that point. there was a significant amount of blood in the car. not enough to suggest that the person was, in fact, dead. >> my daughter was out there somewhere, and i was hoping i would get a call from her, any day, any minute. no call came. >> investigators found five shell casings at the end of the 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 rifle. >> knowing megan had been assaulted with this ak-47, again, sends 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 an opportunity to better understand how crashes happen. >> the recorder, a small onboard