The federal government has documented a pattern of sexual and other violent assaults among patients at the psychiatric unit of a city-run Brooklyn hospital where a woman died in June on the floor of the emergency waiting room while staff members ignored her.

After a yearlong investigation, the Department of Justice portrayed the unit at Kings County Hospital Center as a nightmarish place where patients were not treated for suicidal behavior, were routinely subdued with physical restraints and drugs instead of receiving individualized psychiatric treatment, and were frequently abused by other patients.

The details are laid out in a 58-page report to Mayor Michael R. Bloomberg that was made public on Thursday.

The investigators found that the psychiatric service operated like a prison. The report said that instead of meaningful treatment and diagnosis, the patients received frequent visual checks by the staff, and that even when patients were supposedly under watch, violence and attempted suicides occurred.

Among the most serious incidents the report documented were an October brawl among six patients that left one needing surgery, and an autistic patient being forced to perform oral sex in November. The report also included allegations that a woman was raped and that a 14-year-old was forced to engage in oral sex by a 16-year-old.

All four incidents occurred after the highly publicized death of Esmin Green, a Jamaican immigrant with a history of depression, who collapsed on the floor of the emergency waiting room after waiting nearly 24 hours to be seen. A surveillance video showed Ms. Green, 49, lying on the floor for nearly an hour; during that time, a guard came in to check on her by wheeling his chair along, and another staff member prodded her with a foot.

“While perhaps unique in the extent of the harm that resulted, the tragic case of Ms. Green typifies the patterns of inadequate care and treatment,” reads the report, from Loretta King, an acting assistant attorney general, and Benton J. Campbell, the United States attorney in Brooklyn.

The report, a summary account of the federal investigation that resulted from a 2007 lawsuit by the New York Civil Liberties Union and others, found at least three cases, including Ms. Green’s, when employees falsified records to hide their neglect.

The report became public when Alan D. Aviles, president of the city’s Health and Hospitals Corporation, convened a news conference on Thursday to announce that “radical changes” had been made at Kings County, which treats many of the city’s most severely mentally ill. While questioning some details of the report, he admitted that the unit “too often failed” its patients.

At the hospital’s new $153 million building in central Brooklyn, he announced the replacement of its top two administrators and the addition of 200 medical personnel to its 600-member staff.

Mr. Aviles also outlined new protocols for screening emergency-room admissions, using nonuniformed security officers trained in crisis intervention rather than hospital police. Mr. Aviles noted that in Ms. Green’s case, two guards had looked in on her but decided that she was not their responsibility.

“They clearly felt disconnected from the treatment team,” Mr. Aviles said. “This says something very damning about the model.”

Mr. Aviles said the hospital had cut the average time in the emergency department to 8 hours from 27, and that the number of patients waiting seldom exceeded 25 now, compared with 50 or more on occasion.

“It would be disingenuous of me to suggest that we could prevent all such future incidents, but we can do better,” he said.

Stu Loeser, a City Hall spokesman, said that the mayor believed that the Justice Department report raised “serious issues” but that the changes Mr. Aviles announced “go a long way to addressing many of the conditions.”

The Justice Department’s report said conditions at the psychiatric unit were “highly dangerous and require immediate attention.” It added: “Substantial harm occurs regularly due to K.C.H.C.’s failure to properly assess, diagnose, supervise, monitor and treat its mental health patients.”

The report said that many patients were admitted with “catch-all” diagnoses and that the staff used “boilerplate forms and checklists” rather than writing “individualized narratives.”

The report said that patients were often left in restraints for the two-hour limit even though they had changed their behavior, suggesting that the confinement was punishment rather than therapy. And investigators found it was common to administer injections of more than one antipsychotic medication simultaneously, despite the risk of side effects and overdosing.

In one case, a patient’s treatment plan did not address his obesity, high blood pressure and diabetes, until he had a stroke, according to the report.