(CNN) -- Dr. Bruce Ivins, the former government scientist blamed for a string of deadly 2001 anthrax attacks, behaved oddly and was "sarcastic and nasty" to his wife in the final weeks of his life, police documents said.
Former biodefense researcher Bruce Ivins killed himself in July, authorities say.
Ivins, 62, committed suicide last summer as federal agents were closing in on him, police said.
When Ivins died of an overdose on July 29, federal prosecutors were preparing to present the results of their probe of the anthrax attacks to a grand jury.
The anthrax letters killed five people and sickened more than a dozen just after the September 11, 2001, terrorist attacks. The letters, filled with bacterial spores, were sent to Senate Democratic leaders and news organizations. Those who died were two Washington postal workers, a New York hospital worker, a supermarket tabloid photo editor in Florida, and a 94-year-old woman in Connecticut.
Ivins spent more than 30 years as a civilian microbiologist at the Army's biological research laboratory at Fort Detrick, Maryland, where he was trying to develop a better vaccine against anthrax.
He died after overdosing on Tylenol, according to documents released Monday by police in Frederick, Maryland, and posted on the Web site of the Frederick News-Post newspaper.
The drug destroyed his liver, but Ivins' wife declined to put him on the list for a transplant, saying she did not believe her husband would want one, the records said.
Ivins regained consciousness after being taken to the hospital, according to the investigative reports. "When asked, 'Did you intentionally try to commit suicide?' patient nodded yes," said medical records cited in the reports. In addition, the reports said Ivins grew so agitated when his blood pressure improved that nurses had to administer an anesthetic.
It was not known how the Tylenol entered Ivins' body, the report said, although investigators determined he bought Tylenol PM on two occasions at a local supermarket, both on July 24 -- three days before he was found unresponsive at his home. He also refilled prescriptions for psychiatric medicines that day, but none of those pills was missing, authorities said.
A letter from Ivins' wife, Diane, to him was found on his bedside table after he was taken to the hospital July 27, according to the documents. In it, she tells her husband she is "hurt, confused and angry about your actions over the last few weeks. You tell me you love me but you have been rude and sarcastic and nasty many times when you talk to me. You tell me you aren't going to get any more guns then you fill out an online application for a gun license."
She also notes Ivins has been "going into work at odd hours, and walking in the neighborhood late at night," and says she is concerned he is not following medical advice to reduce stress.
On the back of that note, investigators said, Ivins wrote, "I have a terrible headache. I'm going to take some Tylenol and sleep in tomorrow. - Bruce." A portion is scribbled out, and then Ivins wrote, "Please let me sleep. Please."
Diane Ivins told police in an interview that she had also written that she knew her husband had nothing to do with the anthrax attacks and had never doubted his innocence, according to the Frederick News-Post.
Bruce Ivins' attorney, Paul Kemp, and some of Ivins' coworkers have also maintained his innocence, saying that the stress of the investigation -- and not guilt -- drove Ivins to take his own life.
At the hospital, FBI agents told police they knew that Ivins, his wife and "many members of the general public" were aware that he was under investigation and surveillance in connection with the anthrax incidents. The FBI agents did not enter the hospital, but asked that Ivins' condition be reported to them, the documents said.
The investigative reports also detail an earlier incident in March 2007 when Ivins overdosed on alcohol and Valium, citing a report from the medical examiner's office. While authorities call it a previous suicide attempt, the reports note Diane Ivins maintained her husband was not attempting to kill himself, saying he "had new medication and that she believed he took the wrong one by mistake." Ivins was taken to a hospital emergency room, but was not admitted, according to the documents.
At the time Ivins died, he was under a temporary restraining order sought by a social worker who had counseled him in private and group sessions. He also was hospitalized in the weeks leading up to his death for psychiatric examination after he threatened to kill co-workers, investigators "and other individuals who had wronged him," according to documents released in the case.
Federal prosecutors named Ivins the culprit in the anthrax attacks after his death.
Court records released by authorities showed that Ivins was "the custodian of a large flask of highly purified anthrax spores that possess certain genetic mutations identical to the anthrax used in the attacks." The government had taken steps in the weeks leading up to Ivins' death to restrict his access to his lab.
But critics point to the fact that then-Attorney General John Ashcroft publicly declared another Fort Detrick scientist, Steven Hatfill, a "person of interest" in the anthrax attacks. Hatfill was never charged, but sued over the matter, settling with the government for $5.8 million. His case has fueled skepticism about the allegations against Ivins.
In November, the U.S. Supreme Court threw out Hatfill's libel lawsuit against The New York Times over reports linking him to the anthrax probe. A federal appeals court had concluded Hatfill was a "public figure" and failed to prove the reports were "malicious."
The Frederick Police Department closed the case involving Ivins in November, according to the documents.
CNN's Kevin Bohn contributed to this report.