(CNN) -- Hundreds of inmates in Mississippi whose fight among themselves spiraled into a riot were back in their cells Monday afternoon, leaving authorities to mourn the death of one guard and express thanks that things didn't turn out worse.
"When we first ... learned of the situation, I had a high degree of anxiety because there were so many guards who were unaccounted for," Adams County Sheriff Chuck Mayfield said, praising the efforts of law enforcement and those with the private company that runs the facility. "I know it when I see it when something is handled correctly."
By Monday afternoon, all of the roughly 2,500 inmates at the Adams County Correctional Facility in Natchez were secure in their cells on lockdown, which Mayfield said will continue indefinitely as the investigation continues.
It was a far different scene about 24 hours before.
Mayfield said that, about 2:40 p.m. Sunday, a fight broke out either among members of one gang or between members of rival factions in a prison yard and soon ballooned out of control. With a core group of about 300 inmates involved -- meaning most others were simply caught up in the chaos -- the disturbance quickly spread through the grounds.
"It turned into a mob mentality, and ... it just expanded so quickly," the sheriff said.
Sometime early in the riot, a guard was assaulted and ended up on the roof of a building, Mayfield said. That guard -- later identified as Catlin Carithers, 24 -- was brought out through the facility's gates within an hour, only to be later pronounced dead due to blunt head force trauma, according to the county coroner.
The disturbance continued for hours more around the western Mississippi facility, which houses illegal immigrants from around the region who are serving time after convictions for both violent and nonviolent crimes. The Tennessee-based Corrections Corporation of America operates the facility and employs all those within.
At one point, inmates pulled out some mattresses, rags and other materials into a prison yard and started a fire. Others used an array of weapons, such as mop and broom handles, in their fight.
Meanwhile, the facility's employees at once tried to maintain order and take cover. Mayfield said earlier Monday that at least 24 or 25 hostages were being held at one point.
County and state authorities were on site within an hour to maintain the perimeter and help the Corrections Corporation of America (CCA) bring the situation under control, according to Mayfield, who noted that FBI agents were also there.
No gunshots were ever fired, and Mayfield praised the "restraint" by law enforcement. Authorities did use "pepper balls," which the sheriff said are shot from something akin to a paintball gun.
"The whole thing was probably over by 11 or 11:30 p.m. Sunday," at which point all the inmates had been forced out into a prison yard, Mayfield said. But it wasn't until 3:30 a.m. Monday that every prisoner had been searched and brought back to his housing unit.
In addition to Carithers, about 10 workers at the facility were injured, including one who suffered head trauma and was transported about 100 miles northwest to the University of Mississippi Medical Center in Jackson, according to the sheriff. CCA, meanwhile, has reported that 16 of its staffers at the prison were treated and released from the hospital.
Four inmates had to be taken to area emergency rooms for treatment -- for injuries such as a stab wound, a concussion and rib injuries -- though Mayfield said he didn't think any of them needed to be admitted. CCA had said three inmates received such treatment.
The sheriff stressed that the public was never in danger, as the riot was confined within the facility and there were no breaches of its perimeter.
While he didn't know what exactly caused the riot, Mayfield did say that, "from the outside looking in, I can't see anything that would have prevented it." He lavished praise on the decisions made by Corrections Corporation of America and law enforcement, saying, "I don't think they could have handled it any better."
The sheriff added that the facility has "not had anything of this magnitude at all" since opening in 2009.
"This could have happened anywhere, anytime," Mayfield said.
Yet the American Civil Liberties Union said the riot wasn't surprising because companies like the Corrections Corporation of America "have incentives to cut corners even at the expense of decent and safe conditions"; they employ "too often poorly paid and trained" staff; and they run facilities with conditions that "are often woefully inadequate."
"This weekend's riot should make clear to Mississippi and every other state that for-profit incarceration must end," the advocacy group said in a statement. "We need to save taxpayer money by ending the nation's addiction to incarceration, not give money to private companies whose profit depends on locking up as many people as possible."