The Army scientist believed to have committed the 2001 anthrax killings exhibited classic "offender behavior," sources told FOX News on Monday as officials said he had an obsession with a sorority less than 100 yards away from the New Jersey mailbox where the toxin-laced letters were sent.
Officials tell FOX News that in the days following the mailings of anthrax-laced letters, Bruce Ivins exhibited erratic behavior such as mood swings, pronounced anxiety and a preoccupation with the media.
Authorities also confirmed reports Monday that Ivins was obsessed with the Kappa Kappa Gamma sorority, which may indirectly explain one of the biggest mysteries in the case: why the anthrax was mailed from Princeton, N.J., 195 miles from the Army biological weapons lab the anthrax is believed to have been smuggled out of.
U.S. officials said e-mails or other documents detail Ivins' long-standing fixation on the sorority. His former therapist has said Ivins plotted revenge against those who have slighted him, particularly women. There is nothing to indicate he was focused on any one sorority member or other Princeton student, the officials said.
Despite the connection between Ivins and the sorority, authorities acknowledge they cannot place the scientist in Princeton the day the anthrax was mailed. That remains a hole in the government's case. Had Ivins not killed himself last week, authorities would have argued he could have made the seven-hour round trip to Princeton after work.
Ivins' attorney, Paul F. Kemp, did not immediately respond to a message seeking comment Monday, but has asserted his client's innocence and said he would have been vindicated in court.
Katherine Breckinridge Graham, a Kappa alumna who serves as an adviser to the sorority's Princeton chapter, said Monday she was interviewed by FBI agents "over the last couple of years" about the case. She said she could not provide any details about the interview because she signed an FBI nondisclosure form.
However, Graham said there was nothing to indicate that any of the sorority members had anything to do with Ivins.
"Nothing odd went on," said Graham, an attorney.
Kappa Kappa Gamma executive director Lauren Paitson, reached at the sorority's headquarters in Columbus, Ohio, initially told an AP reporter Monday afternoon she would provide a comment shortly. She did not answer subsequent phone messages or e-mails seeking a response.
Some of the scientist's friends and former co-workers have reacted with skepticism as details about the investigation surfaced. They questioned whether Ivins had the motive to unleash such an attack and whether he could have secretly created the powder form of the deadly toxin without co-workers noticing.
Princeton University referred questions about Ivins to the FBI. The university does not formally recognize sororities and fraternities but chapters operate off campus.
Local police in both Princeton Borough and Princeton Township said Ivins' name did not turn up on any incident reports or restraining orders.
Kappa Kappa Gamma also has chapters at nearby colleges in Maryland, Pennsylvania and Washington. One official said investigators were working off the theory that Ivins chose to mail the letters from the Princeton chapter to confuse investigators if he ever were to emerge as a suspect in the case.
Investigators were able to link Ivins to the letters using new genome technology.
Researchers looked at samples of cells from the victims to identify the kind of anthrax Ames strain that killed them, a government scientist said Monday. They noticed very subtle differences in the DNA of the strain used in the attacks than in other types of Ames anthrax.
Spores taken from envelopes used to mail the anthrax, as well as from the sites where they were sent, were also scrutinized.
With that, investigators linked the specific type of anthrax back to Ivins' biological weapons lab at Ft. Detrick in Frederick, Md., where he oversaw its use and handling for research.
"It had to do with the very specific characteristics in the DNA of the letters and what was in Bruce's labs," said the government scientist who is close to the investigation. "They were cultures he was personally responsible for."
The scientist spoke on condition of anonymity because he is not authorized to speak to reporters.
The scientific discovery gave the FBI its first solid break in one of the nation's most high-profile unsolved crimes after years of pointing the finger at the wrong suspect. Combined with other evidence, the Justice Department is expected to close the case this week, concluding Ivins was the mastermind and sole criminal behind the attacks that killed five and sickened 17 others in the weeks following 9/11.
Ivins took a fatal dose of acetaminophen — the active drug in Tylenol — as federal authorities monitored his movements and prepared to charge him with the murder from anthrax poisoning in the weeks after the 9/11 terror attacks.
Dozens of other researchers in Ivins' lab also had access to the type of Ames strain used in the attacks, the scientist said, meaning the DNA alone is not enough to prove his guilt.
Investigators have said they used other evidence to build the case against Ivins, including looking at who had access to the poison or the labs at the specific time it was mailed. Those details are expected to be spelled out in sealed court documents that are expected to be released this week if the Justice Department ends the investigation, possibly as early as Monday or Tuesday.
Court recordings obtained by the New York Times found that Ivins' therapist feared he was behind the attacks.
"As far back as the year 2000, the respondent has actually attempted to murder several other people ... 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," social worker Jean Duley said during testimony on July 24.
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."
A senior law enforcement official said Sunday that victims' families were waiting to be briefed at FBI headquarters in Washington as soon as prosecutors agree to end the investigation.
Meanwhile, Ivins' brother, Tom Ivins, said the Army scientist thought he was immune from prosecution.
“He had the tendency I understand which made him do these things,” Tom Ivins told FOX News on Monday. "He had this idea in his mind he’s above the law, and nobody is.”
Although the Army lab where Ivins worked had long been on the FBI's radar, scientists were unable to pinpoint the specific strain used in the attacks until about a year ago.
The FBI recruited top genome researchers from across the country and encouraged them to do groundbreaking work to identify and isolate the type of anthrax in the attacks. At least $10 million was spent on the research in what the scientist called the FBI's most expensive and scientifically compelling case to date.
The new genome technology that tracked down Ivins was either not available or too expensive to use often until about three years ago. It also looked at the DNA of the anthrax still in the envelopes that began showing up at congressional offices, newsrooms and post offices soon after Sept. 11, 2001.
The science is known as DNA fingerprinting. Although any two samples of anthrax bacteria will likely share roughly the same DNA structure, there are tiny differences from sample to sample. Scientists used those "fingerprints" to identify the source of the anthrax that killed five people.
In the years since scientists mapped the human genome, computer speeds have increased dramatically, making this process easier and less expensive. DNA fingerprint analysis that not too long ago would have taken years can now be done in days.
The government scientist said the FBI knew the DNA evidence linked Ivins to the attacks for at least a year. However, prosecutors worried that because the genome technology was so new, it might be questioned and eventually thrown out if the case against Ivins ever went to trial. Researchers tested it for many more months to make sure its conclusions were reliable.
Even so, its use in the anthrax case will probably spark scientific debate on how strongly it can be used to help solve crimes, the scientist said.
He predicted few would be able to argue with its conclusions — namely, identifying the type of Ames strain used. Still, the scientist said, some researchers will probably note the DNA does not alone give the government a smoking gun or other surefire case-closer.
FOX News' Catherine Herridge and the Associated Press contributed to this report.