The man put a loaded gun to his sister's head on Friday, but when he pulled the trigger it only clicked and no shot was fired, according to newspaper Göteborgs Posten (GP).
The sister had travelled home to see her brother because she was concerned he was not well. When they met outside his apartment in the centre of the city she attempted to calm him down, but instead he turned on her with the gun.
"This was of course a terrible experience for her. It remains to be seen why it didn't fire. The weapon is subject to a technical investigation," prosecutor Johan Udén told GP.
The brother has now been arrested and is suspected of both attempted murder and serious weapons crimes. He will also undergo a psychiatric evaluation.
The man has previously been convicted of weapons, drugs-related and violent crimes.