Arthur O. Anderson, a medical doctor and scientist at the U.S. Army Medical Research Institute of Infectious Disease at Fort Detrick, said Duley's description of Ivins doesn't match his impressions of a man with whom he worked for many years.

"The remaining allegations about murderous ideas and plans sound so foreign to me that in the absence of contemporaneously documented evidence I would have to consider them items of Ms. Duley's vivid imagination or information fed to her by the people she communicated with outside the therapeutic environment," Anderson wrote in an e-mail to the News-Post. "It is not at all surprising to me that a patient whose therapist is serving as a double agent 'therapist' and 'accuser' would become very angry with the therapist and might make some rather dramatic expressions of that anger."

The doctor and scientist paused briefly after being asked if he believes Ivins committed suicide.

"Oh, yeah," he said. "I think all of the circumstances put him in a place where he felt he had no place to go."

Anderson said he became aware in June that the FBI had taken items out of Ivins' lab.

"The FBI took all of the stored things in his lab freezer," Anderson said. "They basically destroyed his life's work. I think that's what upset him the most."

Anderson said it is "highly incomprehensible" to him that Ivins would be regarded as the perpetrator in this case simply because he had access to anthrax.

He said he last saw Ivins around July 6. Ivins told him the FBI was stalking him, following him everywhere, Anderson said.

"He was animated and appropriately concerned, but certainly not out of control."

Anderson does not believe Ivins is responsible for the 2001 anthrax deaths.

"Now that he can't defend himself against the allegations, this will play out the way it will play out," he said.

But he firmly believes it wasn't guilt that killed his colleague and friend.

"I think it was the sense of betrayal and complete abandonment by those around him," Anderson said. "He cared so much and had so much pride in the work he did -- I don't think he could handle that sense of abandonment."

Maryland's chief medical examiner, Dr. David Fowler, confirmed Saturday that the cause of Ivins' 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, according to the AP.

Kimberly Thomas, a forensic examiner with the Maryland Office of the Chief Medical Examiner, would not comment Saturday on results from Ivins' autopsy or confirm Dr. Fowler's statement.