WASHINGTON — More than a dozen people climbed out of theirs cars on the George Washington Memorial Parkway Tuesday evening to help pull out victims of a shuttle bus crash and right the bus that had overturned on the side of the road, according to one witness.

“It was pretty amazing,” said James Joyner, a professor at the Marine Corps Command and Staff College in Quantico, who was driving behind the bus in the Mount Vernon area at the time of the wreck. The head-on collision caused the bus to tip over.