Three teachers at a secondary school in northwestern Bosnia were killed in a shooting by a colleague, local media reported.
The gunman used an automatic rifle to kill the school employee before shooting himself, Bosnian police said, adding that he was in hospital in critical condition.
Initial reports in local media suggested that the gunman was a janitor at Sanski Most school.
The shooting occurred during a summer vacation in Bosnia.
Police said they received reports that a man opened fire on the school at around 10:00 local time (08:00 GMT).
Adnan Beganovic, a police spokesman for the region, told reporters that the gunman tried to commit suicide and was seriously injured.
Police did not elaborate on whether there was a motive, but Bosnian media reported that the employee, who had been suspended, opened fire at a school committee meeting.
He was taken to hospital in the town of Banja Luka.
Bosnian media said the school director, secretary and English teacher were killed in the attack.