The perpetrator is described as a white male, age 20 to 35. He allegedly threw rocks at cars from highway overpasses and roadsides in Richland County, The (Columbia) State reported.
The sheriff's department said it has received 10 reports of rock-throwing incidents since Jan. 12, including eight on Sunday night.
Most of the incidents resulted only in damage to cars but an incident Jan. 12 injured two people, authorities said.
"This individual needs to be stopped before he seriously injures or kills someone," Sheriff Leon Lott said.
The suspect is thought to be driving a white, older model pickup truck