>> somebody at the mcstay home had searched for getting passports to mexico. >> then just weeks later, what appeared to be a major break in the case. >> authorities are pouring over security tapes. >> new video could show the family crossing the mexican border. is it the mcstays? >> this surveillance footage showing what appeared to be a family of four crossing on foot into mexico on february 8. the very same night the mcstay's isuzu trooper was found near the border. >> we're getting a story, we found the car at the border and we've got a family that looks like them walking across the border. so they may have left voluntarily. >> while detectives pursued that theory, those that knew the mcstays insisted those people in that video were not the mcstays.