Three staff members of a high school in the western Bosnian town of Sanski Most were killed on Wednesday when a school employee shot them.
Police were notified at 10:15 AM (0815 GMT) that a man had opened fire at the school with an automatic rifle, the police spokesman for Una-sana canton, Adnan Beganovic, said, adding that the shooter killed the school dean, the secretary and a teacher.
"The suspect tried to take his own life and was gravely injured," Beganovic said. He was transferred for emergency treatment in the nearby town of Banja Luka. An investigation is underway.
The school had not yet reopened from the summer holidays so no children were involved.
N1 TV, citing witnesses, said that a janitor who had a history of disagreements with the management and was under disciplinary proceedings, sought out specific people and shot them. Reuters could not immeditely verify that report.
Mass shootings are comparatively rare in the Western Balkans which is awash with weapons that remained in private hands from wars in the 1990s.
In July, a war veteran in neighbouring Croatia shot five people including his mother in a nursing home and wounded six others.

Trump backs down on Greenland tariffs, says deal framework reached
Death toll in Karachi mall fire climbs to around 50, official says
Rescuers search for survivors after landslide at New Zealand campsite
Israeli fire kills 11 Palestinians, Gaza medics say
Trump says US will not use force to acquire Greenland
