Reports say a 20-month-old child is among those killed.
The Post and Courier of Charleston reported the shooting happened about 10 p.m. Monday at a house in Walterboro.
Colleton County Fire and EMS director Barry McRoy said three people died and five others were wounded.
Walterboro police are investigating. A dispatcher told The Associated Press that investigators are at the scene and not available to comment. She was not aware of any arrests. The State Law Enforcement Division is assisting.
Calls to McRoy, a state police spokeswoman and Coroner Richard Harvey were not immediately returned Tuesday morning.