“Nicholas’ tragedy illustrates the dangers and horrors of relying on our broken parole and correctional systems to address a mental health crisis,” the society said in a statement on Wednesday morning. “This outcome underscores the New York City Department of Correction’s inability to safeguard the youngest people in its custody.”

Diane Struzzi, a spokeswoman for the Department of Investigation, declined to comment beyond acknowledging that agency was conducting an inquiry, noting that the case was an active matter.

Elias Husamudeen, the president of the Correction Officers’ Benevolent Association, said in a statement that the officers would “be given the best legal representation possible to ensure their rights are fully protected under the law.”

“They are innocent until proven guilty, just like anyone else in our justice system,” he added.

The episode is the latest in the troubled history of the aging jail complex, which has long been plagued by violence, abuse, neglect and mismanagement at levels that have made it among the most notorious correctional facilities in the United States.

In October, the City Council approved a plan to close Rikers Island within seven years and to replace it with what officials envision as safer, smaller and more humane jails that will become a model for the rest of the country.

Mr. Feliciano was in the Elmhurst Hospital Prison Ward on Tuesday, according to city jail records. He was on a respirator with no brain activity, the people with knowledge of the matter said. He was arrested on Nov. 19 on a parole violation and was being held at the complex’s George R. Vierno Center when he tried to hang himself.

One of the people with knowledge of the episode said that Mr. Feliciano had been in a fight the day he attempted suicide. After the fight, he was moved from the general housing area to the intake cell block, where he appeared to be in distress before he tried to hang himself.