A 15-year-old male student at Fallston High School pricked at least 17 other students with a diabetic needle, according to the Harford County Sheriff's Office.
The incident happened between 7:30 and 10:40 a.m. Thursday. Students went to the school nurse, who advised them to see their doctors.
Though parents were eventually informed in a robo-call, a parent of a sophomore, who declined to be identified, said he found out his son was one of the affected students and took him to Johns Hopkins for evaluation.
"They said they're not going to be able to determine anything for 3-6 months," he said.
The school district is investigating while a separate criminal investigation is being conducted by the sheriff's office.
The student has not been charged.
**Editor's Note: The Harford County Sheriff's Office said at least 17 students were pricked. Harford County Public Schools released a statement that said they were "aware of approximately 20 students."