The anthrax case that plunged U.S. residents further into a state of fear following the Sept. 11 attacks took another strange turn last week when the FBI?s prime suspect killed himself.

The case that captivated the nation?s attention has a few ties to the state of New Jersey. In 2001, six people in New Jersey became ill when anthrax-laced letters were mailed out to unsuspecting victims. Across the rest of the country, five were killed and 11 were sickened.

Some of the letters were routed through a post office in Hamilton. For three-and-a-half years, the post office was closed for an investigation and cleanup.

Now that investigators say they know who carried out the deadly attacks, they are trying to figure out how Bruce Ivins, an Army scientist, went undetected as he allegedly plotted the crimes.

Federal investigators say that DNA from the bodies of those killed after being exposed to the anthrax eventually led them to Ivins, who killed himself last week as he was about to be charged.

Investigators have also wondered why the letters containing the anthrax were mailed from Princeton - nearly 200 miles from the Army lab where the anthrax is believed to have been smuggled from.

They now say that Ivins was obsessed with a college sorority that had a chapter less than 100 yards from the mailbox.

Multiple U.S. officials tell the Associated Press that Ivins had been obsessed since his own college days in Cincinnati with the sorority Kappa Kappa Gamma.

An adviser to the Princeton chapter confirms that she's been interviewed by the FBI in connection with the case. Still, authorities can't place Ivins in Princeton on the day the anthrax was mailed.

Ivins? attorney has asserted his innocence and says his client would have been vindicated in court.