One prisoner strangled another to death while other inmates cheered the killing. Two convicts escaped a dilapidated building by walking out an open door. Maximum-security detainees freely roamed hallways, beating and threatening others.

Violence has roiled the Mississippi prison system for more than a week, with state corrections officials imposing a statewide lockdown and a county coroner declaring that gangs in the prisons have launched an all-out war against one another.

At the center of the chaos is the Mississippi State Penitentiary at Parchman — one of America’s most notorious prisons. Since July 2019, seven prisoners have been killed by fellow inmates at what is supposed to be the most secure facility in the state. In the prior eight years, there were four inmate killings.

The current violence comes after years of neglect by state officials, who allowed conditions at Parchman to deteriorate when federal courts ended oversight of the facility in 2011, according to an investigation by the Mississippi Center for Investigative Reporting and ProPublica.

Inmates described themselves as being prey to prison gangs who control the supply of contraband drugs and weapons, bedding, food and cellphones. Photographs and videos reviewed by the news organizations show the most dangerous inmates, identified by their red-and-white striped uniforms, walking freely outside their cells, with no guards in sight.

A video purporting to show the killing of a Parchman inmate on Jan. 3 shows inmates shouting and cheering.

Parchman’s descent has put at risk the safety of corrections officers, the investment of hundreds of millions of dollars of Mississippi taxpayer funds and the health of the inmates the state is charged with protecting, the investigation found.

Corrections officials last year failed to fill hundreds of positions available for guards. In a Sept. 6 email obtained by the Mississippi Center for Investigative Reporting, a correctional officer, Terrence Shaw, told state lawmakers how dangerous it had become working in Unit 29, Parchman’s maximum-security unit.

A building at Unit 29 that should have at least five officers had only two, and some buildings had only one, he wrote. “The National Guard army should have been called in several years ago.”

“Staff morale is down, staff quitting left and right,” Shaw wrote. “All staff working deserve a pay increase that is fit to live.”

Inmates and experts alike say the current violence in no small part arises from the prison’s sheer state of disrepair. Building facilities — water, lights, sewage — are crumbling. The‌ ‌prison’s‌ drinking ‌water‌ ‌has violated the Safe Drinking Water Act dozens of times, ‌and‌ the Environmental Protection Agency has cited the ‌prison’s sewage‌ ‌system‌ for three years for violating the Clean Water Act, documents‌ ‌show.‌‌ ‌Parchman’s‌ ‌accreditation‌ ‌by‌ ‌the‌ ‌American‌ ‌Correctional‌ ‌Association,‌ ‌which‌ ‌sets‌ ‌standards‌ ‌for‌ ‌prisons‌ ‌across‌ ‌the‌ ‌country,‌ ‌lapsed in 2017.‌‌