The knifeman was a patient at the clinic, which serves both outpatients and those committed involuntarily for treatment.
According to local police, he had injured himself and three others with a knife before police were called to the centre shortly before midday on Friday.
“The police travelled to the scene where they found, as reported, a wounded person, as well as the perpetrator who was armed. The police were forced to use lethal fire,” Jenny Widén, a press spokesperson, told Sweden’s TT newswire.
Joakim Kenndal, a spokesman for Sahlgrenska University Hospital, which runs the clinic, said there was a shortage of staff capable of disarming the man.
“Normally we would not treat high-risk patients there,” he explained.
According to the hospital, one man, presumably the perpetrator, had received life-threatening injuries, while a man and two woman were seriously wounded but in a stable condition.
Sweden’s prosecutor’s office has launched a routine investigation into whether the police officer who fired the weapon used excessive force to immobilise the man.