Once inside, the man reportedly approached three female 7th-graders.
"Classes had already changed, and the three students came back to their lockers," principal Greg Hicks said. "He scared the girls so badly and he said, 'I'll come back on Monday.'"
Person County sheriff's officials are currently looking for the individual. They said they do not have a detailed description.
Parents said they are not at ease about the situation.
"It's scary, and you wonder how someone can enter the school that easily," one parent said.
Sheriff's officials are interviewing the three girls and using a K-9 unit in the search.
Authorities are expected to be at the school again on Monday.
Anyone with information is asked to contact the Person County Sheriff's Office.