UTICA, N.Y. (AP) — Three former prison guards from upstate New York are facing trial for the fatal beating of a Black inmate who was handcuffed at the time. A prosecutor described the event as an act of “sheer, unimaginable brutality” to the jury on Tuesday.

The individuals, Mathew Galliher, Nicholas Kieffer, and David Kingsley, are charged with murder and first-degree manslaughter for their roles in the death of Robert Brooks. This incident occurred at the Marcy Correctional Facility on December 9 and was partly recorded on body-camera footage. These men are among ten corrections officers who faced indictments in February, charged with murder or lesser offenses.

During his opening remarks, Onondaga County District Attorney William Fitzpatrick informed the jury they would see distressing videos depicting the guards’ treatment of Brooks. He emphasized each defendant’s direct involvement in the incident.

“They ceased to be corrections officers and acted like a gang,” Fitzpatrick stated. “They took turns—collectively and individually—punching him, kneeing him, using pepper spray, choking him, restraining him, and binding his legs.”

Brooks was dead within an hour, before he even unpacked, Fitzpatrick said.

At 43, Brooks had been incarcerated since 2017, serving a 12-year sentence for first-degree assault, and was moved to Marcy from a nearby facility that night. The videos, which sparked widespread outrage, display officers hitting Brooks in the chest with a shoe and lifting and dropping him by the neck.

Defense lawyers contended that the prosecution would not successfully demonstrate that their clients acted with malice or a depraved indifference to human life as stipulated by the charges. They urged jurors to scrutinize the specific actions of their clients on that particular evening.

“The prosecution is attempting to tie Nicholas Kieffer to the actions of others, suggesting to you that he is somehow responsible via association,” said his attorney, David Longeretta. Kieffer applied a “minimum amount” of pepper spray to Brooks to gain his compliance, the lawyer said.

Galliher’s attorney, Kevin Luibrand, said his client has been charged with murder, in large part, for shackling Brooks’ legs to keep him from kicking.

“Mathew Galliher didn’t harm Robert Brooks. He didn’t hit him, he didn’t strike him, he didn’t encourage others to strike him, he didn’t deny him medical care,” Luibrand said. “He didn’t do anything that contributed to the death of Robert Brooks.”

Fitzpatrick, the special prosecutor, says Brooks died of a massive beating that broke a bone in his neck, ripped his thyroid cartilage and bruised several internal organs. He also died as a result of repeated restrictions to his airways, which caused brain damage, and choking on his own blood.

Fitzpatrick said Brooks was beaten three separate times as soon as he arrived at the prison, the last being the fatal beating in the infirmary caught on the silent body-camera footage.

A fourth corrections officer is scheduled to go on trial for second-degree manslaughter in January.

Six guards indicted in February have since pleaded guilty. Three more employees have agreed to plead guilty to reduced charges and are cooperating with the special prosecutor.

Fitzpatrick also is prosecuting guards in the fatal beating of Messiah Nantwi on March 1 at another Marcy lockup, the Mid-State Correctional Facility. Ten guards were indicted in April, including two who are charged with murder, in Nantwi’s death.

Both prisons are about 180 miles (290 kilometers) northwest of New York City.