The shooting took place around 10 a.m. on Wednesday in the north-western town of Sanski Most.

The alleged shooter was taken to hospital in the town of Banja Luka after apparently trying to commit suicide.

According to Radio Free Europe/Radio Liberty (RFE/RL), police from the Una-Sana Canton confirmed the details of the shooting, adding that the attacker, a worker at the school, shot three colleagues with an automatic rifle.

Adnan Beganović, a spokesperson for the Una-Sana Canton police, was quoted as saying by Reuters that the suspect killed the dean of the school, a secretary and a teacher.

“He [the attacker] tried to commit suicide and was seriously injured,” he said.

The British Daily Mail newspaper, citing local media, wrote that the gunman was involved in disagreements with the management and had been under disciplinary proceedings when he decided to attack the victims.

Mass shootings in the Balkans region are rare, despite it being awash with weapons left over from the Yugoslav wars of the 1990s. However, in May last year, 10 people died when a 13-year-old boy opened fire at a school in the Serbian capital, Belgrade.