WASHINGTON — Army scientist Bruce Ivins had custody of highly purified anthrax spores linked to the 2001 attacks that killed five and access to the distinctive envelopes used to mail them, the government declared yesterday, releasing a stack of documents to support a damning though circumstantial case.

Ivins, a brilliant but deeply troubled man who committed suicide last week, was the anthrax killer whose mailings rattled the nation in the worst bioterror case in American history, just a month after the September 11, 2001, terror attacks, federal prosecutors asserted. They were backed by court documents that were a combination of hard DNA evidence, suspicious behavior, and, sometimes, outright speculation.

Ivins’s attorney said the government was “taking a weird guy and convicting him of mass murder” without real evidence. Senator Grassley, a Republican of Iowa, called for a congressional investigation.

Ivins had submitted false anthrax samples to the FBI to throw investigators off his trail and was unable to provide “an adequate explanation for his late laboratory work hours” around the time of the attacks, according to documents that officials made public to support their conclusions.

Investigators also said he sought to frame unnamed co-workers and had immunized himself against anthrax and yellow fever in early September 2001, several weeks before the first anthrax-laced envelope was received in the mail.

Ivins killed himself last week as investigators closed in, and U.S. Attorney Jeffrey Taylor said at a Justice Department news conference, “We regret that we will not have the opportunity to present evidence to the jury.”

The scientist’s attorney, Paul F. Kemp, heatedly dismissed that comment.

“They didn’t talk about one thing that they got as result of all those searches,” he said. “I just don’t think he did it, and I don’t think the evidence exists.”

Mr. Taylor conceded the evidence was largely if not wholly circumstantial but insisted it would have been enough to convict.

The prosecutor’s news conference capped a fast-paced series of events in which the government partially lifted its veil of secrecy in the investigation of the poisonings that followed closely after the airliner terror attacks of September 11.

The newly released records depict Ivins as deeply troubled, increasingly so as he confronted the possibility of being charged.

“He said he was not going to face the death penalty, but instead had a plan to kill co-workers and other individuals who had wronged him,” according to one affidavit. In e-mails to colleagues, Ivins described a feeling of dual personalities, the material said.

Officials disclosed yesterday they had restricted his access to the biological agents last September.

Ivins had sole custody of highly purified anthrax spores with “certain genetic mutations identical” to the poison used in the attacks, according to an affidavit among a stack of documents the government released, all seemingly pointing to his guilt. Investigators also said they had traced back to his lab the type of envelopes used to send the deadly powder through the mail.

The FBI’s investigation had dragged on for years, tarnishing the reputation of the agency in the process. Investigators had long focused on Steven Hatfill, whose career as a bioscientist was ruined after then-Attorney General John Ashcroft named him a “person of interest” in 2002. The government recently paid $6 million to settle a lawsuit by Mr. Hatfill, who worked in the same lab as Ivins.

Mr. Taylor said yesterday that investigators concluded in 2005 that Mr. Hatfill couldn’t have had access to a crucial flask of anthrax spores.

Authorities say that language Ivins used in an e-mail days before a second round of anthrax attacks was similar to the messages in anthrax-laced letters received soon after by Democratic Senators Tom Daschle and Patrick Leahy.

In the e-mail, Ivins wrote that “Bin Laden terrorists for sure have anthrax and sarin gas” and have “just decreed death to all Jews and all Americans.” The letters to Messrs. Daschle and Leahy said: “WE HAVE THIS ANTHRAX . . . DEATH TO AMERICA . . . DEATH TO ISRAEL.”

Yesterday’s documents were released as FBI Director Robert Mueller met privately with families of the victims of the attacks to lay out the evidence officials said the agency was preparing to close the case.

As for motive, investigators seemed to offer two possible reasons for the attacks: that the brilliant scientist wanted to bolster support for a vaccine he helped create and that the anti-abortion Catholic targeted two pro-choice Catholic lawmakers.

“We are confident that Dr. Ivins was the only person responsible for these attacks,” Mr. Taylor told a news conference at the Justice Department.

Noting that Ivins would have been entitled to a presumption of innocence, Mr. Taylor nevertheless said prosecutors were confident “we could prove his guilt to a jury beyond a reasonable doubt.”

The events in Washington unfolded as a memorial service was held for Ivins at Fort Detrick, the secret government installation in Frederick, Md., where he worked. Reporters were barred.

More than 200 pages of documents were made public by the FBI, virtually all of them describing the government’s attempts to link Ivins to the crimes.