One of the officers assaulted at a Tennessee prison Sunday has been released from the hospital, and the other two officers involved are in stable condition, according to the Tennessee Department of Correction. The department, with the help of the Tennessee Bureau of Investigation, continues to investigate the attack, which included one officer being taken hostage at a prison about 60 miles southwest of Nashville.

Officer Lester Ball was treated and released overnight, while officers Jesse Shockley and Paul Nielsen remain hospitalized in stable condition, the department said in a news release.

"During the course of the disturbance, the three officers were stabbed multiple times. Two of those officers, Ball and Nielsen were removed from the unit immediately," the release states.

"Officer Jesse Shockley was held hostage for approximately three hours. TDOC’s Special Operations Unit responded and regained control of the unit without force at approximately 7:00 pm, allowing Officer Shockley to be removed without further incident. All three officers were taken by helicopter to a local hospital. There were no other injuries."

Sunday at 4 p.m., 16 inmates created a "disturbance" at the Turney Center Industrial Complex, a prison in Only, Tenn. The release states the inmates' attack was "unprovoked" and the inmates "may have ties to a security threat group." Security threat group is a department euphemism used to describe gangs.

"This attack was really driven by, I think, started as a verbal confrontation between an officer and an inmate and it escalated from there. Totally no indicators that anything was going to happen. Just a person who was serving a lot of time who made a bad decision," Tennessee Department of Correction Commissioner Tony Parker said during a news conference Monday afternoon.

"When we arrived at the facility, we established conversation with the inmates. I wouldn't call it negotiations; I think it was more of a conversation that was taking place between myself and some other people at the facility."

Late Monday the department released the names of all 16 inmates reportedly involved in the disturbance. Inmates Michael Mills, Nicholas Durant, Victor Sparkman and Ronnie Akins were specifically highlighted by the department and were moved to Riverbend Maximum Security Institute in Nashville, but the department didn't specify how each inmate participated in the incident.

There is no excuse for inmates attacking officers or taking anyone hostage, said Jeannie Alexander, a former prison chaplain who now heads an advocacy organization called No Exceptions Prison Collective. For months, Alexander said, there have been numerous complaints by prisoners about conditions in the unit where this incident occurred.

"You cannot continue to crush people and dehumanize people and not expect consequences at some point," Alexander said.

Parker confirmed the assaults happened at Unit 3 of Turney Center, a standard prison unit with 128 inmates and one officer. Parker called that a general staffing ratio throughout the state system.

Unit 3 is not officially a gang unit, but there are gang members housed in the area, Parker said.

Alexander said she and others have received numerous reports from insiders about alarming conditions inside the unit. It may not have an official designation as such, but Alexander and others have heard for months this unit has issues with gang violence.

"Nobody listens to prisoners. This is the problem … they’ll tell you if something's coming down the pike. They’ll tell you if something is going to go off, but no one ever believes them," Alexander said.

Alex Friedmann, a former inmate who is now the associate director of the Human Rights Defense Center and managing editor of Prison Legal News, also received reports about incidents at this unit.

He said housing gang members together can contribute to more violence inside prisons, similar to what happened at Turney Center.

"The problem with that approach is that housing gang members together concentrates their numbers and thus their power base; non-gang prisoners in the unit are at greater risk of being victimized, and concentrating gang members in one area makes it more difficult for staff to control them," Friedmann said.

"Our contacts at Turney Center have informed us about dangerous conditions and high levels of violence in Unit 3, and certainly prison officials should have been aware of that problem."

Information obtained by The Tennessean shows there are 43 correctional officer vacancies at Turney Center currently. Of the 309 total officer positions available, 266 are filled. Out of 439 positions, including administration, teaching, medical and clerical posts in addition to officers, 376 are filled, according to the data obtained.

Sunday the inmates involved were moved to Morgan County Correctional Complex, a maximum security facility. Apart from the four moved to Riverbend on Monday, the rest remain at Morgan County. Most of the roughly 1,600 inmates at Turney Center are classified as medium security.

Parker said he didn't know the last time an officer was taken hostage in a Tennessee prison.

"Fortunately, that's one of those occurrences that happen very rarely. But in the corrections field they do happen from time to time, and it's just an unfortunate reality of the department we work for and corrections in general."

The Tennessee State Employee Association said in a statement, "The recent series of events affecting the lives of officers working within the Tennessee Department of Correction has TSEA very concerned about officer safety within the department."

Assault numbers in state prisons are down, Parker said. But for years, the department has faced legislative and media scrutiny over how an assault is defined. After Tennessean investigations, legislative hearings and a recommendation from the American Correctional Association, the department in 2016 changed how assaults are defined.