She said it was too early to speculate on the motive but said there were indications that the shooting was gang-related.
"There is absolutely nothing that indicates terrorism," Brehm said.
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She said that at least two people were killed at the scene and several others taken to a hospital.
One witness told Swedish broadcaster SVT that two men entered the restaurant and started shooting with automatic weapons.
"I didn't have a chance to think about what happened. Then I saw that my friend was bleeding. I tried to stop the bleeding as well as I could with my hand," said the witness, who didn't give his name.
Police said the shooting happened inside a restaurant called Var Krog och Bar, which means "our tavern and bar" in Swedish. According to its website, the restaurant opened in 1995 and also has a sports bar and a night club that's open on Fridays and Saturdays.