The shooting occurred about 10 p.m. Monday in Walterboro, about 40 miles west of Charleston. Colleton County Coroner Richard Harvey said the victims were from Walterboro and were related to each other, though he did not know the relationships.
Harvey named the victims as 20-month-old Shaniyah Burden, Charles Kittrell, 45, and Christopher Powell, 21. Kitrell died at the scene and the other two in separate hospitals.
The shooting happened outside a small, beige bungalow in a neighborhood of compact houses along a side street.
Ginni Keeling, 22, who identified herself as a cousin of the family, said they often played cards and watched television in the front yard of the house.
"I've been over here since I was 13 years old. I ain't never seen anything like this," she said.
Family members told The Post and Courier of Charleston the victims were playing cards in the front yard when a car pulled up and opened fire.
Keeling said she'd left the scene about 15 minutes before the shooting with her two young children and she got a call from another relative at the scene, telling her about the incident.
Keeling said she had no idea what the motive behind the shooting might be. She drove one of the people at the scene to a local hospital because the person was hyperventilating, Keeling said.
No arrests have been reported.
Officers were looking for a black car with one headlight, Walterboro Police Capt. Ken Dasen said. He referred other questions to the State Law Enforcement Division. A SLED spokeswoman said she couldn't immediately provide details.