A man who died in a Rikers Island cell would still be alive if the exhausted correction officer supervising him had not left his post 15 hours earlier, the detainee’s family charged in a legal notice filed Monday.

Robert Jackson, 42, was found dead inside a housing unit at the Anna M. Kross Center at around 10 p.m. on June 30, according to jail records.

Before leaving his post, the officer in the area had been working for over 20 hours without relief and begged to be replaced, according to the Correction Officers’ Benevolent Association. The officer is facing disciplinary charges, according to multiple jail sources.

More than 1,000 officers have been calling out sick on any given day over the past several months, forcing others to work double and sometimes triple shifts.

“The city locked Robert Jackson in a cell, where he was unable to help himself, and then abandoned him there,” said attorney Josh Kelner, who is representing Jackson’s family. “This isn’t just about one officer who walked off his job. It’s about a system so broken that the officer could be gone for hours and no one replaced him.”

The filing of the notice of claim, a precursor to a lawsuit, came as a group of local elected officials and representatives from public defender groups toured several facilities Monday at the jail, rocked by recent deaths and staffing shortages.

The officials witnessed an apparent suicide attempt and clashed with union leaders as one politician called on Gov. Kathy Hochul to send in the National Guard to help run Rikers, which a federal monitor recently deemed plagued by “disorder and chaos.”

The de Blasio administration initially tried to block the visit to the beleaguered lockup, according to the Daily News.

“What I have seen today clearly puts the message at the forefront that decarceration must happen and must happen now,” said Assemblymember Phara Souffrant Forrest (D-Brooklyn), a prime sponsor of the “Less is More Act,” which limits when people on parole can be re-jailed.

Ten Deaths This Year

State Sen. Jessica Ramos (D-Queens) said she was appalled to see dead cockroaches, fecal matter and rotting food during her tour.

“I can’t begin to tell you the deplorable conditions,” she told reporters. “There are at least one dozen men per cell. We witnessed someone trying to commit suicide just a little while ago.”

A man inside the punitive segregation unit inside the Otis Bantum Correctional Center tried to hang himself, according to the politicians.

“A man called me over and pointed to someone who jumped up on the bars and tried to use a bedsheet to kill themselves … I called a guard over. I think [the detainee] was OK,” said Assemblymember Jessica Gonzalez-Rojas (D-Queens).

Ten detainees have died in custody this year, with five believed to have taken their own lives, according to jail records.

Self-harm — including suicides — at Rikers Island and other local lockups spiked last summer as COVID-19 ravaged New York, WNYC/Gothamist and THE CITY reported last week.

Ben Fractenberg/THE CITY

The head of the union representing correction officers and several of his allies briefly interrupted the news conference held by the politicians.

“They witnessed today inmates all over the place,” said COBA President Benny Boscio Jr. “Breaking out of housing areas. In the corridors. This is our reality every single day.”

He later joined the politicians and advocates after some of them urged him to come to their side of the street.

A Call for Help

Before the visit, some detainees threw trash into hallways and refused to move back to their housing units as they tried to talk to the politicians, according to Joe Russo, president of the Assistant Deputy Wardens/Deputy Wardens Association.

But jail officials weren’t able to clean up some spots like the intake area inside the Otis Bantum Correctional Center, according to Russo and some of the elected officials.

“Even with advance notice, whatever attempts there were to window-dress were unsuccessful,” said Assemblymember Zohrain Mamdani (D-Queens). “We spoke to incarcerated people who have been without medical aid, who have been on hunger strikes for four days. I spoke to someone who came May 26th and is yet to see recreation.”

Hours after the politicians toured Rikers, City Councilmember Robert Holden (D-Queens) sent a letter to Hochul urging her to have the National Guard fill in for missing correction officers.

“The City Council, federal monitor, union, advocates and inmates themselves have all raised the alarm,” he said. “Nothing changes. As governor, you can acknowledge the emergency we are facing and mobilize the National Guard.”

‘A Prayer Warrior’

As for Jackson, the Queens man was in jail facing burglary charges, according to the New York Post, which first reported the circumstances of his death.

“It’s sad because he had his whole life to live,” his uncle, Willie Cobe, 55, told THE CITY. “He was a good person. We went to church together. He was a prayer warrior.”

The city medical examiner has not yet determined the cause of death. The correction union notes Jackson’s death occurred approximately 15 hours after the officer left his post. Officers must remain in place until they are relieved, according to department rules.

Jail officials failed to provide Jackson “proper supervision and care,” according to the filing, which says the family is seeking $15 million.

On Friday, the jail system’s chief medical officer, Dr. Ross MacDonald, took the unusual step of asking the City Council to seek federal assistance.

He cited overflowing intake pens where in at least one spot the city’s jail oversight board found that detainees were not given regular meals or recreation and were forced to sleep without blankets.

“The overcrowding leads to people kept for prolonged periods in temporary spaces such as showers, at times standing in feces,” MacDonald wrote.