and i didn't see him for the rest of the day. >> reporter: in a murder so up close and personal -- so vicious -- boyfriend nathan naturally became a person of interest immediately. when officers brought him to dallas police headquarters, detective ellzey was more than ready to ask nathan some very personal and specific questions about his relationship with shelley. >> are you a virgin? >> yeah. >> is shelley a virgin to your knowledge? y'all ever discuss sexual intercourse? never? she's been in your bedroom before with the light off. what do ya'll do? >> we were sitting there playing video games. >> you never tried anything sexual with her? [ shakes head ] >> she never tried anything sexual with you? did you kiss her? >> no, never. >> you never kissed her? she's been your girlfriend two months and you never kissed her? [ shakes head ] cop: why? it's weird.