Eventually, one officer knelt down and held his face. Another helped him up. He stumbled and was quickly flanked by two officers who led him away, the video shows.

A total of five officers were taken to hospitals for treatment. One was stabbed 12 times and another suffered a ruptured lung, union officials said.

One officer was still in the hospital on Friday evening, a spokesman for the state corrections agency said in an email.

The union condemned the violence during a press conference on Thursday, saying the attack appeared to be premeditated and an “attempted murder.”

The union’s executive board said in a statement released Friday that it was “stunned, appalled and angry at the level of brutality in this video, but unfortunately not surprised.”

The statement said the union had warned the state’s prison officials about “something like this.”

“Our officers continue to be injured,” the statement said. “This horrific video speaks for itself. Change must happen, and fast.”

State prison officials declined to comment on the release of the video on Friday.

A spokesman said they would continue to rely on a statement released Thursday that said operations at the prison had been changed to ensure the safety of all workers and residents there; the affected inmates had been transferred to other state prisons; and the Worcester District Attorney’s Office was conducting a full criminal investigation.

The violence erupted around 6:20 p.m. Wednesday as officers made their hourly rounds of the general detention unit at the maximum security prison on Route 2. At the time, there appeared to be only about six inmates in the room. Most were hanging around the perimeter.

The video also shows a guard being attacked from behind by an inmate leaning against a wall. The inmate punched him in the throat and made stabbing motions. As the officer grabbed the inmate and threw him to the ground, a second inmate joined the fight. He eventually took the officer down, put his ankles around his neck and forced him into a headlock.

A second officer runs in, pulls the prisoner away from him, who is stabbing the other guard, and wrestles and struggles with him until a third officer steps in, nearly stopping the violence. At that moment, the video shows a third inmate jumping in and starting to throw punches.

Dark smears that look like blood can be seen on the floor. A little more than a minute after the first blow, about ten officers stream into the room one after the other and pounce on the struggling guards and inmates to break up the fight.

Union officials said the video was “a shock to the conscience” and called for a comprehensive evaluation and review of all security-related policies, procedures and protocols in all state prisons.

“These men who were attacked were fighting for their lives,” the union’s statement said. “They were fighting for themselves, they were fighting for each other, they were fighting to go home to their families, and they survived.”

The union executive committee’s closing statement said: “ENOUGH IS ENOUGH. Our members never want to be here again.”

You can reach Tonya Alanez at [email protected]. Follow her @talanez.