put in the envelope. dropped in a mailbox. and people would die. >> robert stevens is the first to die. >> you know, it doesn't say natural causes or accident on my husband's death certificate. it says homicide. >> originally from england, in the '70s stevens and his wife maureen had moved to florida. he worked for american media incorporated. a tabloid publisher. >> there's no one that can say they didn't like him. he was just full of life and he loved everybody. >> in early october 2001, stevens has what seems like the flu. two days later, slurred speech. and a trip to the hospital. >> she said, it's anthrax. now, i'm getting shivers thinking about it. and she said, "the cdc had been informed, the fbi, and the president has been informed." and i was in shock. >> robert stevens dies the next day. anthrax had shut down his vital organs. >> he was just the perfect person for me and i do miss him. you know, my heart's still not in one piece yet. >> lab work reveals the type of anthrax that killed stevens. it's called the aim strain. with terrifying implications. >> the aim strain was a lab strain. it was not out there in the wild. >> david willman, a pulitzer prize winning investigative reporter, is the author of a recent book on the anthrax attacks. >> the fact that this is a laboratory strain told them this is a bioterrorism event. >> a week later anthrax-filled letters start showing up at major news organizations in new york. >> anthrax. another infection. this time at nbc news in rockefeller plaza. >> the attack letters have a chilling message. death to america. death to israel. allah is great. >> i was a postal inspector team leader during the case. >> former u.s. postal inspector thomas dellafera helped lead the investigate from the early days. i just want to ask for your instant reaction at the time. >> initial reaction, looks like another al qaeda event. it's a follow on attack. initially that's kind of where my head was. >> three days after the nbc letter, capitol hill. >> the letter is addressed to senate majority leader tom daschle. it's opened. the white powder spills out. >> we don't know how many people came in contact with the letter. there were 40 people in my office at the time. >> a preliminary testing with portable devices in the senate office building says it's anthrax. it was game on. >> i was covering the hill back then. and i can tell you, it felt surreal. congress and the supreme court shutdown and mail delivery to the white house was cut off. all three branchs of government. >> you can't overstate the drama, the shock and awe power of that event. >> a massive multiagency investigation called amerithrax goes into full force. and another anthrax letter, this one addressed to senator patrick leahy of vermont is found, unopened. >> no one thought, whoa, any letter addressed to a member of congress has to come through the brentwood mail handling facility just a few blocks away in northeast washington. so none of the postal workers were given the benefit of immediate nasal swabs or preemptive doses of an antibiotic. >> two postal workers, joseph curseen and thomas morris jr. will die. >> we had letters but we still couldn't prove where it was -- where it originated from. >> the fbi's ed montooth now retired, would eventually become lead agent. >> was it coming from al qaeda? was it coming from a foreign government? was it, you know, a homegrown issue? >> whoever mailed the anthrax had covered his tracks. >> you're really hoping for a partial fingerprint at a minimum or some sort of dna. and we had none of that. we had absolutely none. >> the anthrax powder offered hints after being examined by one of the pentagon's experts on biological weapons. a scientist named bruce ivins. >> there was no one who was really more experienced at growing, purifying and handling, preparing anthrax spores at ft. detrick than bruce ivins. >> ivins reported his findings. extremely pure. extremely high concentration. these are not garage spores. in other words, the work of a pro. >> it would be somebody that would be working with this for some, you know, reason. may it be research or vaccinations or advancement of some sort of scientific project. >> hints also in the wording. allah is great. would a real jihadi mix arabic and english? >> the specialists at the fbi, they concluded in their profile within a couple months' period of time that they thought it was a domestic actor, not a foreign actor. >> the fbi thought the killer might be hiding in plain sight. so the fed sent this e-mail to the american society of microbiologists asking its members, scientists, for help. it is very likely that one or more of you know this individual. someone with legitimate access to dangerous germs and a high degree of technical knowledge. someone whose personality might be described as stand-offish. out of 42,000 members, there is one response. >> i just thought, oh, no. i might actually know the person. >> nancy haigwood. a microbiologist with a hunch. >> i also had conviction that i really needed to call the fbi. >> murder by mail? >> this was certainly murder by mail. . 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>> bruce ivins. >> bruce ivins. a scientist at usamriid. the u.s. army medical research institute for infectious diseases. ft. detrick, maryland. this is the pentagon's main lab for studying biological weapons. to develop protective vaccines. ivins is an expert on anthrax. in fact, he's supposedly helping federal agents. >> in january of 2002, bruce ivins was in the thick of it. >> what the feds do not see is the hidden side of bruce ivins. e-mails where he says, i am being eaten alive by paranoid, delusional thoughts. >> bruce ivins has led a double life. >> psychiatrists will later describe ivins as a secretive, paranoid, resentful and rage filled man. >> he was a guy who had a definite dark side to him that no one else knew about. >> i met bruce in chapel hill, north carolina. >> it was the mid-'70s. nancy haigwood was a graduate student at the university of north carolina. bruce ivins was there, too. ivins asked incessantly about haigwood's sorority, kappa kappa gamma. he seemed obsessed. >> every time he talked to me he'd mention it. finally i said, bruce, that's enough. >> as their careers took shape over the years, ivins kept in touch. shortly after the anthrax attacks, he e-mails these photos of himself with what he calls the new infamous aim strain of anthrax. >> he wanted his former colleagues and friends to know that he was doing important work. >> one detail stands out. >> he said he was working in the containment lab. and he wasn't wearing gloves. and that is a biosafety hazard. we just don't ever do that. and what that is, is a, to me, a sign. i'm immune. >> haigwood has distrusted ivins for years, beginning with a 1979 incident in grad school when her lab notebook, all her data, went missing. >> it's absolutely critical. it's your only copy. >> and it disappeared? >> and it disappeared. i came in one day and it wasn't there. and i -- i just panicked. >> the next day, an anonymous letter telling her that the notebook was in a mailbox. >> and so i called the police. we got the notebook back. >> how would you characterize it? a very mean prank? >> it was a cruel joke, i would say. and i thought, the only person i could think of that would do something like this, this odd, might be bruce. >> why you, though? >> you know, it's funny. because i felt like i was one of the few people who was friendly to bruce. >> three years later, 1982, haigwood with her ph.d. was working in suburban washington. by coincidence, she lived in the same neighborhood where bruce ivins had just moved from. one day haigwood came home to find her house vandalized. >> the sidewalk, the fence and the car were sprayed with red spray paint. >> even after she whitewashed it, you could see kappa kappa gamma. >> because of the kappa connection i immediately thought of bruce ivins. >> five months later this letter to the editor of the local "fredrick news post." a response to an article about abusive hazing at colleges. as a member of kappa kappa gamma, the author is incensed at vitriolic attacks on hazing. hazing strengthens the mettle of pledges and builds loyalty and the all-important weeding out process, signed nancy haigwood. there was just one problem. >> i didn't write this letter. >> do you believe in hazing? >> certainly not. >> after calling the newspaper to disavow the letter, she called ivins. >> and i said, this can only be you and you have to stop. >> what did he say? >> he said he didn't do it. but, of course, then i knew he was lying. >> did you think he was obsessed with you? >> clearly he was obsessed with me. yes. >> four years later, 1987, ivins filled out a medical history form at usamriid. asked about memory change. trouble with decisions. hallucinations. improbable beliefs and anxiety. ivins put a question mark. >> there was no follow-up. at no point did the army ever evaluate bruce ivins' mental fitness to handle anthrax. the approach was just to defer to his status as a ph.d. scientist as a trustworthy individual in their estimation. everybody knows that he wouldn't harm a flea. >> nancy haigwood isn't so sure. the stolen notebook. the vandalism. and the phony letter to the editor. it's enough for her to contact the fbi. >> i just thought, i just need to tell these people and they need -- they need to look into this. >> that there was a creepy side to bruce ivins? >> yes. a deceptive side. >> but for the next 4 1/2 years, her tip is low priority. >> we didn't know how to put it in any context. we had nothing to bring it together with. so at that time it sort of was tabled, if you will. >> a few months later, the fbi is making some progress. the anthrax letters, all with the same postmark, are traced back to a mailbox here in princeton, new jersey. it's contaminated with spores. but why here? across the street from an ivy league university? did the killer use the travel agency? rent from one of the real estate companies? or eat at the red onion delicatessen? >> all that was documented was the mailbox with the spores is at 10 nassau street. >> no one paid attention to a small office a few doors down. the office for a sorority, kappa kappa gamma. ♪ [ cellphone rings ] cut! 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[ male announcer ] write your story with the new citi simplicity card. no late fees. no penalty rate. no worries. get started at citisimplicity.com. no lat i've tried it.lty rate. no worries. but nothing's helped me beat my back pain. then i tried this. it's salonpas. this is the relief i've been looking for. salonpas has 2 powerful pain fighting ingredients that work for up to 12 hours. and my pharmacist told me it's the only otc pain patch approved for sale using the same rigorous clinical testing that's required for prescription pain medications. proven. powerful. safe. salonpas. i tell you what i can spend. i do my best to make it work. i'm back on the road safely. and i saved you money on brakes. that's personal pricing. anthrax is odorless. tasteless. and the fatal dose is so small, you can't even see it. so to protect against terrorists or rogue nations, scientists at usamriid, the army's biodefense tech lab, work. it's here where federal investigators turn for help. to the hot suites with the world's deadliest germs. >> obviously we're going to need to use people in the community to help us analyze our materials. ? but the expertise to solve the crime may also have the expertise to commit it. >> so, we did an expedited background investigation on them, and offered them polygraphs to say to them, if you want to work on our evidence, we're going the need you to do this. >> bruce ivins seems to pass, though experts will later question those results. >> it was essentially a set of three questions that was do you know who did this, were you involved in it, or did you provide the anthrax that was used in the mailings? >> one of usamriid's anthrax specialists, ivins holds two patents on what he hopes will be a new, genetically engineered vaccine. >> the bringing online of the next generation anthrax vaccine would have been the ultimate validation of his scientific expertise. >> colleagues say ivins is hard working and dedicated. he volunteers for the red cross. others describe him as socially awkward, craving acceptance. he's the guy who writes clever poems for the office parties. he juggles. >> there's an expression that took hold among colleagues and friends. yeah, he's odd. he's quirky. but that's just bruce being bruce. >> but he's not just quirky. in e-mails, he writes about two bruces. i'm a little dream self-short and stout. i'm the other half of bruce when he lets me out. when i get all steamed up, i don't pout. i push bruce aside, then i'm free to run about. >> if he becomes offended by someone and believes and concludes that they have done him wrong in some way, he will go after them. >> from the beginning, ivins implicates current and former colleagues. >> and said, you know, you need to investigate this person because he has the skill. he has the ability. he has access to everything he needs to do this. oh, by the way, he happens to live up in the area where the mailbox was used for the mailing. >> the tips from ivins go nowhere. but the federal investigation does focus on a former usamriid scientist named steven hatfill. he had worked here in the late '90s. investigators say eight people flagged hatfill to the fbi. >> i want to look my fellow americans directly in the eye and declare to them, i am not the anthrax killer. >> on his resume, hatfill claims a working knowledge of america's former biological weapons programs. the fbi says a witness reports hatfill claimed to have prepared and used anthrax as a weapon in the late 1970s while studying in southern africa. >> i have never, ever worked with anthrax in my life. >> the suspicion is fueled by hatfill's job at saic, a government contractor. he works on biological weapons defense. one project hatfill proposed about risk of anthrax sent through the mail is proposed a single letter being sent to government agencies and news agencies. >> that was very interesting to us in that it is what happened. almost prescient. >> hatfill says it's all for training first responders, doctors and army medics on how to handle biological threats. >> so it became a challenge for us to sort out why are they here? are they -- are they legitimately for the -- his biopreparedness, his emergency preparedness work, or is this something more nefarious. >> raising the stakes, he had several prescriptions for cipro, the drug of choice to treat anthrax. reporters are also looking at hatfill. when federal agents search his apartment, the press choppers in, thanks to leaks from inside the investigation. >> they were quite, i think, anxious to get that word out to demonstrate that we're on top of this. >> but investigators find nothing that connects hatfill to the crime. so a few weeks later, the fbi comes back with bloodhounds, hoping to find the scent of anthrax on hatfill 11 months after the crime. >> we saw it as, sure, why not? let's give it a shot, right? >> because you didn't have much going at the time? >> well, we were struggling, right? >> two problems with the bloodhounds. first, they can be unreliable. one of the dogs, named tinkerbell, had helped get an innocent man in california charged with serial rape. >> tinkerbell got the wrong guy. then tinkerbell was brought to maryland and tinkerbell was alerting on and essentially fingering steven hatfill as a anthrax killer. >> second, the blood hound search was leaked to the media, quoting an unnamed source "newsweek" says one of the dogs bounded right up to him. the dogs, they went crazy. but everything that the dogs point to, including a lake that the fbi drained looking for evidence turns up empty. >> at some point, it didn't add up. and we backed off the use of the dogs. >> turning up the heat on hatfill, attorney general john ashcroft outs him to the media. >> mr. hatfill is a person of interest to the department of justice. >> hatfill is put under 24-hour surveillance. and will be in the government's sights for several years. >> if i am a subject of interest, i'm also a human being. >> with his career in ruins, hatfill sues the department of justice for the press leaks. >> can your reputation ever be repaired? >> the government will eventually pay him nearly $6 million and acknowledge that for years, they were focused on an innocent man. >> they're in a rough place. if the fbi does not have me as a person of interest, then what does it have? >> the real killer is still out there. well...weird. she won't eat eggs without hot sauce. she has kind of funny looking toes. she's always touching my hair. and she does this dancing finger thing. 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[ male announcer ] stop the madness of treating frequent heartburn. it's simple with prilosec otc. one pill a day. twenty-four hours. zero heartburn. no heartburn in the first place. great. i'm don lemon and here are the headlines this hour. six stream court justices were among the dignities at the red mass in washington. the catholic church services is held every year before the opening of the supreme court term. it is called the red mass because of the color of robes that were worn. critics were also present saying that the attendance is not appropriate with justice department and religion. and 17 people are dead from tainted cantelopes. the cdc says more people could be