he broke into two of them to steal information on kkg's secret rituals. if this guy breaks into sorority houses? >> it shows us somebody who is bold. unafraid. he said in one of our interviews, that gave him power. that gave him a sense of power. >> we asked him about his -- his interests. and he said it's more than an interest in kkg. it's an obsession. >> but why? ivins says it may have begun in college. 40 years ago. >> it goes back to him being rejected for a date by a woman at the university of cincinnati. he never could get over it. and he attributed her rejection of him to her membership in that sorority. >> to investigators, it now makes sense. the princeton, new jersey, mailbox. a few doors down from the kkg office. >> his obsession helps in my mind explain how the mailbox that was used was chosen. >> meeting for coffee with an acquaintance who is wired for the fbi, ivins denies being the anthrax killer. >> i have no clue how to -- how to make a bioweapon and i don't want to know. >> but at the same time, he admits to memory loss. ivins is fallin

we then started doing searches around the street location and came up with a kkg reference.it's about 30 to 60 feet from our box. >> narrator: the kkg administrative offices were actually 175 feet from the mailbox on the fourth floor of an office building. but to the fbi, it was more than a coincidence. >> we knew it was a really big deal. it is a way to connect dr. ivins to that crime, to the location where the letters were mailed. >> narrator: at fbi headquarters, they had something they believed was even stronger- - they thought they had caught ivins intentionally misleading them about the alleged murder weapon, rmr-1029. >> it just showed us his willingness and deliberate attempt to mislead us, and actually tell us mistruths. >> narrator: the fbi had found matches between the anthrax in the letters and one particular source. >> samples start coming back positive. and all of those samples that turn out positive have all been drawn up originally from bruce ivins' 1029 flask. >> narrator: but the sample bruce ivins gave them from rmr- 1029 did not match. to investigators, i

he said it's more than interest in kkg, it's an obsession. >> but why?have begun in college, 40 years ago. >> it goes back to him being rejected for a date by a woman at the university of cincinnati. he couldn't get over it. he attributed her rejection of him to her membership in that sorority. >> to investigators, it now makes sense. the prince ton, new jersey mailbox, a few doors down from the kkg office. >> his obsession helps in my mind explain how the mailbox that was used was chosen. >> meeting for coffee with an acquaintance wired with the fbi, ivans denies being the anthrax killer. >> i have no clue how to make a bioweapon and i don't want to know. >> but at the same time, he admits to memory loss, ivans is falling apart, abusing prescription drugs and alcohol. >> 911, what's the nature of your emergency. >> march 19, 2008. ivans' wife calls paramedics when he collapses at home. >> so you're not sure how long he's been like that. >> i know he was on-line 45 minutes ago with a friend. >> okay. do you know what he said in that conversation? >> it w