The rider on the outbound 6-Parnassus bus line was stabbed in the neck with scissors around 3:32 p.m. on the bus near Market and Hayes streets, San Francisco police Sgt. Michael Andraychak said.
The suspect and the bus driver were in some sort of argument when the passenger tried to calm the suspect down and was then stabbed in the neck, according to Andraychak.
The victim suffered superficial injuries and was treated at the scene, Andraychak said.
The suspect, who has not been identified, was taken into custody.
The bus driver was uninjured and fellow passengers were taken off the bus, which was taken out of service as police continue to investigate the stabbing, Andraychak said.