No one is injured, says police spokesman Mats Eriksson.
The incident is classified as a serious unlawful threat and a serious violation of the Weapons Act.
Several witnesses have called in with observations.
The alarm was received just before 1 p.m.

A young man has been detained on suspicion of firing several shots at a door in an apartment building in northwest Stockholm on Friday, police said.
No one is injured, says police spokesman Mats Eriksson.
The incident is classified as a serious unlawful threat and a serious violation of the Weapons Act.
Several witnesses have called in with observations.
The alarm was received just before 1 p.m.