Friends and colleagues of Ivins were still puzzling today about a man they thought they knew, reports CBS News correspondent Randall Pinkston.
"It would be very difficult to put him in a role of a violent person," said former colleague Bruce Adamovicz. "He just simply didn't have that in him."
Adamovicz, Ivins' former supervisor, says Ivins knew he was under suspicion for the deaths of five people in the 2001 anthrax attacks.
"It's very difficult, given Bruce's personality, he was a very sensitive person, very high strung and it's understandable that these continuing pressures on him would wear him down," Adamovicz said.
But Ivins apparently had a violent side. Just days before he committed suicide, Jean Dudley, a therapist who had been treating Ivins for six months, went to court for a protective order, citing a threat he made in a group session.
"He proceeded to describe to the group a very detailed plan to kill his co-workers," Dudley said. "That because he was going to be indicted on capital murder charges, he was going to go out in a blaze of glory that he was going to take everybody out with him."
Duley testified at a hearing in Frederick on July 24 in a successful bid for a protective order from Ivins. The New York Times obtained a recording of the hearing and posted it on its Web site Saturday.
"As far back as the year 2000, the respondent has actually attempted to murder several other people, either through poisoning. He is a revenge killer. When he feels that he's been slighted or has had - especially toward women - he plots and actually tries to carry out revenge killings," Duley said.
She added that Ivins "has been forensically diagnosed by several top psychiatrists as a sociopathic, homicidal killer. I have that in evidence. And through my working with him, I also believe that to be very true."
Duley told the judge she was "scared to death" of Ivins.
Ivins, 62, who worked at an Army biodefense laboratory at Fort Detrick, took his own life Tuesday as federal authorities were closing in after investigating him for more than a year in connection with the deaths of five people poisoned by anthrax sent through the mail.
Answers to one of the nation's highest profile unsolved mysteries are in documents that could be released as early as this week - and help explain how the government chased the wrong suspect for years.
So far, federal authorities have not formally released details of its investigation into Ivans role in the attacks, Pinkston reports. Legal experts say the government is not required to open its files.
"It is likely we'll never know the full extent of the government's evidence and even if we do we won't what Ivins' response would have been cause he wont have a chance to respond," said Stephen Saltzburg, a law professor at George Washington University, and former justice department official.
If authorities close the case, court documents detailing newly developed scientific evidence that recently led the government to Ivins may be unsealed.
Five people died and 17 others were sickened when anthrax-laced letters began showing up at congressional offices, newsrooms and post offices soon after Sept. 11, 2001.
Former FBI profiler Gregg McCrary told The Early Show, "When you begin to profile the cases you look at all the decisions a offender makes. The choice of weapons, who had access to anthrax, and especially this form of weaponized anthrax."
That, McCrary said, narrowed the search to Fort Detrick (what he called "the right place"), even though the FBI's public investigation of Steven Hatfill led to an embarrassing (and costly) payment.
McCrary thinks the pressure of the investigation may have contributed to Ivins' suicide, but the reasons remain unknown. "Either because he was guilty and didn't want to face that ultimate reality [of five murder charges] or not, we don't know. I think in the days coming it's going to be really important how the government sort of tacitly negotiates the legal issues to make whatever evidence they have available to the public.
"We'd like to know what the evidence really is so we can get a sense of how compelling that evidence may or may not be."
Right now all the relevant grand jury proceedings are under court seal.
"If they declare the case closed that may then pave the way to unseal some of these documents and some of the evidence and we may get the opportunity to get a closer, more detailed look," McCrary said.
After wrongly investigating Army scientist Hatfill, the FBI more than a year ago began looking at Ivins, who worked at the same military lab. Ivins, a decorated scientist who was working on an anthrax cure, killed himself last Tuesday.
Two U.S. officials said victims and their survivors could be briefed as early as Tuesday on the final piece of the bioterrorism attacks that confounded the government.
The Justice Department attributed the break in the case to "new and sophisticated scientific tools" that cost the FBI about $10 million. Investigators said the science focused, in part, on how the anthrax strains were handled and who had access to it at the time of the mailings.
FBI scientists were able to isolate strains used in the attacks, and determined they were not as common as previously thought. And that led investigators to Ivins.
Had the same process been available years ago, it would have cleared Hatfill much earlier, according to two people familiar with the FBI investigation who spoke on condition of anonymity because the case is not officially closed.
The Army refused Saturday to say whether it had been reviewing the security clearance of the chief suspect in the anthrax attacks who had mental problems and killed himself as federal prosecutors were planning to indict him.
Ivins was removed from his lab in Maryland by police on July 10 and temporarily hospitalized, according to court records, because it was feared that he was a danger to himself and others. But it was unclear whether he was still employed by the lab at the time of his death Tuesday.
That raises the question of whether Ivins still had his security clearance and, if so, how he kept it, given that his social worker said Ivins had been viewed as homicidal and sociopathic by his psychiatrist.
Army spokesman Paul Boyce declined to comment on Ivins' case.
Boyce didn't respond to a question on what type of clearance microbiologists at the lab would have to hold.
David R. Franz, a former commander of the Army's lab biological warfare labs at Fort Detrick, Md., where Ivins worked, said Saturday he thought it was "very important that the FBI present their case against Bruce and not just state that the investigation was over because it was him and he's gone."
Franz added, "I'm concerned about what closing this case without conclusive evidence might do to harm our life sciences enterprise. ... I think we as Americans need to see the proof."
Initially, FBI profilers said they probably were looking for a loner with a scientific background. Maybe he had a grudge against the lawmakers and news organizations. Investigators also considered possible links to al Qaeda, the terrorist group behind the 9/11 attacks.
Intensive focus initially settled on Hatfill, who for years accused the government of unfairly targeting him. In late June, the government exonerated Hatfill and paid him a $5.82 million settlement.
With that, the government seemed no closer to solving the "Amerithrax" mystery. But, quietly, investigators were closing in on a different scientist, Ivins.
A murder indictment and the possibility of the death penalty could have produced a high-profile climax to the case. Shadowed by the FBI, Ivins died Tuesday from a Tylenol overdose, leaving the probe in limbo and a nation seeking answers.
"It's a shame the man is not here with us. We might have known more," said Maureen Stevens, whose husband, Bob, was the first anthrax victim.
Former Senate Democratic leader Tom Daschle of South Dakota, said: "I think the FBI owes us a complete accounting of their investigation and ought to be able to tell us at some point, how we're going to bring this to closure." Daschle's office received a letter containing the deadly white powder in 2001.
Among the unanswered questions is why the anthrax was sent. The FBI was investigating whether Ivins, renowned for his work developing anthrax vaccines and treatment, released the toxin to test those cures. Ivins was one of several scientists named in an application for a vaccine patent 18 months before the attacks.
Another puzzle is what finally led the FBI to focus on Ivins a year or so ago. Ivins attracted some attention for conducting unauthorized anthrax testing in the six months following the anthrax mailings, but the FBI focus stayed on Hatfill.
As Ivins' name emerged, so did a portrait of a conflicted, troubled man. His friends knew him as the man who played the keyboard at church, a Red Cross volunteer who was an avid juggler and gardener.
Others saw a darker side. Police recently removed him from work, fearing he was a danger to himself or others. Social worker Duley filed for a restraining order in a Maryland court.
"Client has a history dating to his graduate days of homicidal threats, plans and actions towards therapists," Duley wrote in court documents last week, adding that his psychiatrist had described him as homicidal and sociopathic.
Ivins' brother, Tom Ivins, said he had not spoken to Bruce Ivins since 1985, but acknowledged the possibility his brother may have been the anthrax mailer.
"It makes sense, what the social worker said," Tom Ivins said. "He considered himself like a god."
Ivins' lawyer, Paul F. Kemp, asserted the scientist's innocence and said he would have proved it at trial. Kemp said his client's death was the result of the government's "relentless pressure of accusation and innuendo."
Maryland's chief medical examiner, Dr. David Fowler, confirmed Saturday that Ivins died Tuesday morning at Frederick, Md., Memorial Hospital; that the cause of death was found to be an overdose of acetaminophen, the active drug in Tylenol; and that it was ruled a suicide based on information from police and doctors.