In the House of trade unions in the Swedish city of Malmo skirmish, in which three people were injured, according to Sydsvenskan.
Two wounded young men were taken to hospital in serious condition and are in intensive care.
A third victim, a teenager, suffered minor injuries.
The incident occurred in the Banquet hall of the House of trade unions, where there were 70 to 100 people. Burst into the room and a man asked who hit his brother, and opened fire with a pistol.
According to witnesses, the man fired about six shots and fled the scene.