Ten former prison guards were indicted for the killing of Robert Brooks, a prisoner incarcerated at the Marcy Correctional Facility in Marcy, New York, who was fatally beaten at the prison in December.

A grand jury indicted six officers — Nicholas Anzalone, David Kingsley, Anthony Farina, Christopher Walrath, Mathew Galliher and an unnamed defendant — on felony second degree murder and first degree manslaughter.

The nine defendants charged in the indictment appeared in court on Thursday and all pled not guilty to the charges brought against them. A tenth, unnamed defendant was unavailable to surrender on Thursday and is expected to be arraigned soon. He is not believed to be a flight risk.

The officers are accused of acting with other correctional officers in conduct that “created a grave risk of death to another person, and thereby caused the death of Robert Brooks,” according to a criminal indictment.

Brooks was transferred from the Mohawk Correctional Facility to the Marcy Correctional Facility on Dec. 9, 2024.

Excerpts of body-worn camera footage from four corrections officers were released Dec. 27 by the New York Attorney General’s Office showing the in-custody beating of the 43-year-old inmate.

In the footage reviewed by ABC News, multiple officers can be seen holding Brooks upright on an exam table, with his arms restrained, punching and kicking him in the face, torso and genitals. The beating was described in a deposition by an investigator for the New York Department of Corrections Office of Special Investigations.

Brooks was pronounced dead at a local hospital the day after the beating, according to New York Attorney General Letitia James, whose office is investigating the incident.

The deposition detailed that two sergeants and a nurse watched the attack and neglected to intervene. They were among the 14 prison staffers whom New York Gov. Kathy Hochul ordered to be terminated by the state.

The indictment Thursday said Brooks was allegedly assaulted on two occasions when he arrived at the infirmary by Anzalone, Walrath and the unnamed defendant — despite being restrained.

Upon arriving to the emergency room of the infirmary, Brooks was “restrained, beaten, choked, gagged, forcibly moved and kicked, all with minimal resistance on the part of Mr. Brooks and with no legitimate law enforcement purpose,” the indictment alleges.

Beating and assaults were carried out by the defendants while acting in concert together, the indictment said.

“In addition to the beatings, defendants with depraved indifference, did nothing to restrain each other, did nothing to stop the beatings and failed to immediately order medical assistance for Mr. Brooks,” the indictment said.

Brooks suffered injuries to his head, neck, hyoid bone, thyroid cartilage, torso, liver, spleen and testicles, his air passages were restricted and he chocked on his own blood, resulting in his death, according to the indictment.

Michael Mashaw, Michael Fisher and David Walters were indicted on felony second degree manslaughter. Nicholas Gentile was charged with tampering with physical evidence.

Walrath and the unnamed defendant were also indicted on felony second degree gang assault.

Mashaw, who was the ranking corrections officer in the infirmary, is accused in the indictment of failing to order the beatings to stop and not getting Brooks medical assistance until it was too late to save him.

Fisher and Walters are accused of having a clear line of sight to Brooks, but failing to attempt to stop the beatings or shield him. Walters also allegedly instructed a nurse no not enter the emergency room where Brooks was, the indictment said.

Anzalone and the unnamed defendant are accused of offering a false statement with intent to defraud the state. They wrongfully reported that all force against Brooks ceased when he entered the emergency room of the infirmary, the indictment alleges. The defendants were not aware that their actions were being recorded, according to the indictment.

“Nothing can bring him back to us. Nothing can return to us what these men have taken away. Still, these indictments are a necessary and important step toward accountability. These men killed my father, on camera. All the world could see what happened. Waiting for these charges has been incredibly hard,” Robert Brooks, Jr., the son of Brooks, said in a statement Thursday.

“These men must be fully prosecuted and convicted for what they have done. But even the convictions of these corrections officers for the murder of my father will not be enough. Every person in authority who allowed this system of violence and abuse to exist and continue for so long must also be held accountable,” he said.

The New York State Correctional Officers and Police Benevolent Association issued a statement in December reading, “What we witnessed is incomprehensible to say the least and is certainly not reflective of the great work that the vast majority of our membership conducts every day… This incident has the potential to make our correctional facilities even more violent, hostile, and unpredictable than ever before.”