ran his license plate, and it was a minivan, and it was registered to patrick russo and his wife janet russo: patrick russo? could he be the guy who creeped out all those women? could he also be the killer? his last known address was in a rural area outside austin. so before dawn, unannounced, they paid a visit. it was a pretty drive. but at 4:00 a.m., the detectives weren't exactly taking in the view as they drove to his home. hoping that this could shed light on diane's murder. but remember, all they had was a creepy guy looking for houses for sale. was patrick russo that guy? maybe. maybe not. dawn was hours away when they knocked at his door. the man who woke up to answer it looked like the composite sketch. >>> coming up -- patrick russo seems an unlikely killer. >> i got my ged, i went to college. i studied for theology to become a minister. >> but an odd coincidence. he was in diane's area the day she was killed. >> do you remember ever talking to her? >> reporter: when dateline continues. eporter: when dateline continues. which is why we do everything in our power to make buying a ca