Police said they received reports around 10 a.m. local time (8 a.m. GMT) that a man had opened fire at the school.
Local police spokesman Adnan Beganovic told reporters the shooter was suicidal and suffered serious injuries.
Police did not elaborate on a motive for the incident, but Bosnian media reported that the employee had been suspended and opened fire during a school board meeting.
He was taken to a hospital in the town of Banja Luka.
Bosnian media reported that the school's principal, secretary and English teacher were killed in the attack.
