A spasm of violence at a private prison in Oklahoma lasted just a couple of minutes, but it killed four inmates and injured several others, officials say. The Oklahoma Department of Corrections describes the Saturday afternoon incident at the Cimarron Correctional Facility as a "disturbance" and says staff members in the area responded very quickly, NBC News reports. Officials say the incident, which happened as medium-security inmates were being let out to the exercise yard, left three men dead from stab wounds on Saturday and a fourth man died from his wounds overnight, reports the AP, which notes that up to 300 inmates were involved in a massive brawl at the same facility in June.
It's not clear what sparked the violence at the prison operated by Corrections Corporation of America, which the Wall Street Journal notes is America's largest private prison operator. The 1,720-bed facility was locked down after the incident, and officials say that as a precaution, all other prisons in the state are also on lockdown, the AP reports. The AP also notes that with a homicide rate of 14 per 100,000 inmates, compared to an average of 4 per 100,000 nationwide, Oklahoma has the highest prison murder rate in the country.