Pupils at Townville Elementary School were evacuated after a teenager opened fire, wounding two students and a teacher before he was taken into custody.
None of the victims appear to have life-threatening injuries.
The other students were taken by buses accompanied by police cars to nearby Oakdale Baptist Church, where they were reunited with their parents.
Anderson County Coroner Greg Shore told the Anderson Independent Mail that authorities were also responding to a death "believed to be related" to the school shooting about one-and-a-half miles away.
Townville Elementary had around 300 students last year, according to its annual report last spring.
