An eight-second surveillance video released by Chongqing city police on its Weibo social media account shows the two arguing and grappling with each other in the moments before the bus suddenly veered across oncoming traffic and off the bridge Sunday morning.
Buses in China often have surveillance cameras.
A statement from Wanzhou district police said the 48-year-old female passenger asked the driver to pull over after she missed her stop, but he didn't. She walked up to the driver's seat and scolded him. The driver turned his head back several times arguing.
As the quarrel escalated, the statement said, the woman hit the driver on the head with her cellphone. The driver took his right arm off the steering wheel and fought back. He grabbed her arm when she attacked him again, then hastily steered to the left, sending the bus out of control.
The Chongqing police also posted dashcam video from a nearby car showing the bus colliding with an oncoming vehicle before smashing through a guardrail and falling into the Yangtze, a major river in southwestern China.
The Wanzhou police statement said the behavior of the driver and the passenger seriously endangered public safety and violated the law.
Rescuers lifted the wreck of the bus from the river Wednesday night. Thirteen bodies have been found and two remain missing, the official Xinhua News Agency said.