Sgt. Dan Scott says the suspect boarded the bus with the woman in Culver City, followed her to the back of the bus and forced himself on her late Wednesday afternoon.
A lone witness tried to alert the bus driver that the rape was happening, but it continued for about 10 minutes until the suspect stopped and exited the bus.
Scott says the 18-year-old woman has the mental capacity of a 10-year-old. He says that after the attack, she reported it to the driver.