The South Carolina Department of Corrections identified seven inmates killed in a "mass casualty incident" at a maximum security men's prison on Sunday night.

Officials said in addition to the seven killed, 22 were injured in a series of "inmate on inmate altercations" beginning around 7:15 p.m. The 22 injured inmates were transported for outside medial attention.

As of Wednesday, six inmates were still admitted to outside medical facilities.

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The inmates killed were identified as Raymond Angelo Scott, Michael Milledge, Damonte Marquez Rivera, Eddie Casey Jay Gaskins, Joshua Svwin Jenkins, Corey Scott, and Cornelius Quantral McClary.

The Associated Press reports that most of the inmates were killed by stabbing or slashing.

SC Department of Corrections director Bryan Stirling said the altercation appeared to stem from gang-related conflict over territory, contraband and cell phones.

READ MORE: Lee Correctional prison riot: Seven inmates killed in incident identified in 'mass casualty incident'

According to Department of Corrections records, Milledge was serving time for drug crimes out of Greenville County in 2007.

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His inmate report indicates he was sentenced to 25 years for trafficking in crack cocaine in Greenville County; 25 years for manufacture, distribute or possession of a Schedule III controlled substance in Greenville County; 5 years for a firearms provision in Greenville County; 1 year for possession of illegal drugs in Greenville County; and 10 years for first-degree assault and battery in Marlboro County.

Prison records indicate while incarcerated, Milledge was disciplined numerous times, including for striking an employee, possession of escape tools or paraphernalia, possession of contraband, possession of a weapon, exhibitionism and public masturbation, threatening to harm and employee and possessing or attempting to possess a cell phone.

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According to online court records, Milledge filed a complaint against the Greenville County Sheriff's Office in October 2013 in connection with his 2007 arrest. The complaint claims Milledge's vehicle and the belongings inside were seized after his arrest but not returned to him when he was released on bond 8 months later.

The complaint says in 2013, Milledge still had not received information about the whereabouts of his vehicle and property. A judge dismissed the complaint in December 2013.

Milledge's projected release date was June 20, 2032.

PHOTOS: Officials say 7 inmates died when violence erupted in this SC prison

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