The driver continued on to the next exit as passengers performed first aid on the wounded, he said. The motive for the shooting was not immediately known, and there was no indication the gunman knew any of the victims, Pennings said. The remaining passengers were later driven away by relatives or continued to Northern California on another bus. Pennings called the actions of the driver and the passengers who disarmed the gunman heroic but didn't provide immediate details. Greyhound prohibits passengers from bringing guns, explosives or dangerous chemicals on board its buses or in their luggage, according to its website.