After the shooting around 12:30 p.m., which took place in the front part of the school and not in a classroom, the suspect fled the building and was found hiding by deputies. He was taken into custody.
Both the victim and suspect were described as male teenagers.
The victim was transported to a local hospital for treatment. His condition is unknown.
The school resource officer immediately responded to the shooting and the school went into lockdown, Greenville County Sheriff Hobart Lewis said.
"Everybody went to where they're supposed to be," Sheriff Lewis said. "We conducted lockdown drills with the school district in the past several months, and people kind of call and question and complain while we do those things. Unfortunately, we had to use that."
More than 100 deputies responded to the scene, according to Lewis.
A reunification site is being set up nearby for students to meet their parents.
"All students will be transported at Brookwood Church at 580 Brookwood Point Place, Simpsonville, SC 29681, where parents will be reunited with their student," the district said in a statement, according to Fox Carolina. "Parents will not be able to pick up their student at Tanglewood. Parents will need to have identification in order to pick up their student."
This is a breaking news story. Check back for updates.