“Our working hypothesis is still that the crime was gang-related,” said Thomas Fuxborg, press spokesman for police in the region.
“We have to expect that there may be reprisals.”
To prevent revenge attacks more police officers will be moved into the area over the weekend.
No one has yet been arrested for the shooting. Police have searched with dogs, helicopters and several patrols and some weapons have found close to the scene.
“We will compare them with the shell casings found at the murder scene,” said Fuxborg.
"Today, the gang environment is… I don't want to exactly call it the Wild West, but something in that direction," he said.
"Some years ago, it used to be very strong groups controlling the criminal world, but today we've got more and a lot smaller groups fighting for control of their areas – and that has increased the number of conflicts we see between groups and individuals."
In June a report by Swedish public radio programme Ekot revealed that a number of young people identified by Gothenburg authorities eight years ago as being at risk of joining gang violence have since continued to commit crimes, despite repeated interventions by Swedish social services.