But after confirming the presence of anthrax, law enforcement officials say, Ivins delayed filing a report for three months, in violation of Army protocols.
Ivins reportedly said he took the action because he did not want to cause an uproar.
The renewed focus on Ivins came after the FBI concluded it had been too single-minded in its focus on Hatfill. The Department of Justice agreed in June to a $5.8 million settlement with Hatfill over a lawsuit alleging the government had invaded his privacy and violated his rights.
Until, or unless, the FBI makes public its case against Ivins, his suicide is certain to raise similar questions.
"Could this be another single-minded focus, is this another we think we got him but we don't have him," asked former FBI agent Garrett.
"Is this going to be Hatfill-2?"