>> reporter: holbert was fully cooperative.he car, i need to know about that. >> no, i did not. >> not even touched her? >> no. >> reporter: so, they let him go. if nick holbert was a suspect, he certainly wasn't acting like one. he joined search teams looking for kelli. and even spoke on local tv, expressing his concern. >> she seemed like a really nice and cool person. and i mean, i hate that she's missing. >> reporter: but fayetteville police weren't buying holbert's story. and now, he, too, was a person of interest, along with kelli's husband, mike bordeaux. remember, mike said he was home, in florida, when she went missing. which detectives needed to confirm. >> family put him there, friday night. friends put him there. his alibi checked out. >> reporter: so now, detectives and district attorney, billy west, zeroed in on the last person seen with kelli. >> everything kept coming back to nicholas holbert as the prime suspect. >> so investigators doug into holbert's background and discovered something rather disturbing. >> h