SPARTANBURG, S.C. (AP) _ A man stalking what he thought was an intruder accidentally shot and killed his sister, who was unexpectedly home from school with a sore throat, the deputy coroner ruled.

Harold Leon Wasson, 19, apparently killed 13-year-old Christine Lynn Wasson with a shot to the head from a rifle Tuesday, authorities said.

Wasson told detectives that after returning home, he heard noises in the house, said Lt. Mike Ennis, spokesman for the Sheriff's Department. Loading a .357-caliber rifle, ''he started working his way back through the house,'' Ennis said.

''He said that when he opened (his sister's) door, it wouldn't open all the way. About that time, she stepped from behind the door, and he fired,'' Ennis said.

Spartanburg County Deputy Coroner Richard Seay ruled the shooting accidental.

Investigators don't know whether Christine yelled or jumped toward her brother, but she apparently ''intended to scare him or play a joke on him,'' Ennis said.

No charges have been filed against Wasson. Ennis said ''there are a lot of questions right now that still aren't answered.''