Police have remanded in custody a 52-year-old man suspected of perpetrating the crime. The incident is being investigated as murder, because it had apparently been planned in advance.
Police received a report about the shooting at 1am.
The gunman fired several shots in the restaurant, but their exact number is not yet clear. At the time of the incident, the restaurant was full of customers.
One bystander was injured in the shooting—Matti Koota, who had won a bronze medal at the Youth World Amateur Boxing Championships in 2008, got a bullet to the leg.
The police quickly detained the suspect near the restaurant on the basis of eyewitness reports. The man still had the weapon in his possession. The weapon was without a licence.
In addition to murder, the incident is being investigated as a gun crime, a case of endangering others and grievous bodily harm.
More information about the course of the investigation will be released on Monday.