After the stabbing, police closed Mason Street between Jackson and Pacific to conduct an investigation.
While police were conducting what looked like an arrest, one Asian woman said to our ABC7 camera, "Please help us. They confiscated our video camera. We were taping this whole thing."
Police took two women into custody but did not say if they were suspects or why they were being taken in.
Shortly after the scene, police followed a blood trail leading away from the cable car, up Pacific, and arrested a male suspect just minutes after the incident.
The cable car operator was taken to San Francisco General Hospital and his condition is unknown.