>> reporter: little nervous? >> -- a father to him, yes. >> reporter: or -- or the way -- >> but he -- >> reporter: but the way it was described later was more like you were a mother to him. i mean, you were -- >> well, yes, that was his own -- his own words. >> daniel worried about nathan, he said. saw early red flags in nathan's behavior toward this first girlfriend of his. nathan, he said, seemed obsessed with shelley. maybe dangerously. >> i started to notice that nathan had missed his classes. and finally, i talk to shelley's roommate, ashley, and what she told me shocked me because from her own words, nathan was actually stalking shelley everywhere she goes. and after shelley was murdered, he said, he saw scratches on nathan's body. which, in fact, the police had noticed, too. and then daniel added something very interesting -- he picked up nathan from school on thursday night, that's the day of the killing. it was more than 12 hours before shelley's body was discovered,