"It's a terrible situation to be quite honest," Sheriff Hobart Lewis said at a press conference early Sunday.
Lewis said two Greenville County sheriff's deputies were driving by when they noticed a disturbance at Lavish Lounge just before 2 a.m. and saw a large crowd running out of the building.
The two deputies then turned into the club as people started screaming, heard more gunshots, and then entered the building, according to the sheriff.
There was “active gunfire from inside the building,” Lt. Jimmy Bolt said in an initial statement, and Lewis said all the shots were fired inside.
"There's a lot of shell casings inside," Lewis told reporters.
Fox Carolina reporter Cody Alcorn said a DJ inside the club captured the shooting on a Facebook live video.
Both Lewis and Bolt initially said 12 people had been wounded — with at least four in critical condition, Lewis said — but Bolt later confirmed to Fox News the casualty figure had been revised.
Bolt said there were 10 victims from the shooting and two have succumbed to their injuries. The eight other victims' injuries range from non-life-threatening to critical.
Two suspects are being sought though there is limited information on them, Fox Carolina reported.
The names and precise conditions of the victims weren't immediately released. Lewis said the victims were taken to the Prisma Health hospital in Greenville, many in private vehicles since the facility is "extremely close by."
Multiple forensic units remained at the scene hours after the initial shooting, according to Alcorn.
Lewis said a “very large crowd” was at the nightclub for "some type of concert. A post on Lavish Lounge’s Facebook page advertised a July 4 performance by trap rapper Foogiano.
A booking representative told the Associated Press in a text message that Foogiano was fine and his team was safe.
In late June, Greenville — which has experienced some of the state's highest COVID-19 rates — became the first city to mandate face coverings in South Carolina, where Gov. Henry McMaster has refused to implement a statewide mask requirement.
McMaster reminded South Carolinians last week that he hadn't lifted restrictions on large crowds, and that those operating nightclubs illegally or holding concerts against his orders don't have to be caught in the act to face criminal charges, but instead could be charged weeks later if COVID-19 cases are traced back.
Lewis said at the press conference that he didn't know whether the club had sought an exemption to the governor's order or secured a permit for Saturday night's event, but said it was clear that the club's patrons weren't 6 feet apart.
“It's certainly not the best situation to stop the spread of this virus,” the sheriff said.
The Associated Press contributed to this report.