The man boarded the bus at 120 North Redwood Drive in San Rafael around 8:45 a.m. and stabbed the driver in the face, head and neck with a sharp metal object, sheriff's Sgt. Craig Scardina said.
The county Department of Health and Human Services' Division of Social Services is located at that address. Services offered by the division include employment and training assistance and help with food stamps and health care.
The bus driver was taken to a hospital with injuries that are not believed to be life-threatening, Scardina said.