>> she never said that. >> boy, you sound like mad. you're a damn psychopath. are you like coo-coo-coo and la la land? does [ expletive ] not register to you? >> nothing makes sense. i'm just -- i'm just waiting to wake up. >> that's right. you're waiting to wake up. now, what did you do with the knife? >> i wasn't there. >> nathan, you -- >> i didn't do anything with a knife. >> yeah, you did. >> reporter: detective ellzey made no apology for the aggressive tone of his interrogation. there was more to learn about this closed off young man, for whom questions about knives would have an extra special meaning. >> reporter: coming up -- someone offers a new and unsettling portrait of nathan's relationship with shelley. i talked to the roommate.