A 16-year-old boy was found dead in a car Friday at Cane Bay High School after suffering what authorities described as "a medical emergency."
The Berkeley County Sheriff's Office said there was no danger to other students on the campus 25 miles north of Charleston and west of Goose Creek, which was locked down for a couple of hours.
Authorities were tight-lipped about the incident and did not disclose what the medical emergency was.
The teen has not been publicly identified and no relatives had commented on his death on Friday.
"A 16-year-old student was found deceased in a car ... parked in the student parking lot," Berkeley County Coroner George M. Oliver said in an email Friday afternoon. "An autopsy will be scheduled to determine the cause of death."
Oliver said his office and deputies would continue the investigation.
"Our hearts are with his family and many friends during this difficult time," Principal Tim McDowell said in a statement. Grief counselors will be available for students.
Following the student's death, rumors circulated on social media that the incident may have been a murder-suicide. Authorities said that was not true.
"This was an isolated, single-subject incident," said Chief Deputy Jeremy Baker, a spokesman for the sheriff's office.
One girl who said she was in the school at the time described the situation in a post on Twitter as "very terrible for all students."
"A ton of rumors were going around inside the school and no one was telling us anything and it was scary," she tweeted.
Further information was not available Friday.
Gregory Yee contributed to this report.