During the fight, Ran lost control of the bus and the vehicle broke through a guardrail and plunged into the river with an estimated 15 passengers on board in Wanzhou, Chongqing.
Authorities have released footage of the accident, as recovered from the bus' black box.
The driver, whose left hand was on the steering wheel all the time, used his right hand to turn the bus, taking the vehicle, at a speed of 51kph, into the opposite lane.
The passenger, only identified as a 48-year-old woman with the surname Liu, was angry at the driver for missing her stop, police said. When he refused, she walked up to the front of the bus to confront him.
As she continued to assault him, the driver swerved into oncoming traffic and hit a auto before breaking through the crash barrier and plunging into the Yangtze River, the longest river in Asia.
Leicester leave it late to salvage point against 10-man West Ham
We defended so well for the whole game but particularly for the 55 minutes with one player less. "He will have to have an examination then we will see, of course".
According to the Ministry of Emergency Management, the salvage work was especially hard because of the small size of the bus, the depth of the water, limited visibility and shifting currents that impeded divers.
Rescuers on Wednesday night pulled the bus from the river. A few seconds into the video, a woman is hitting the bus driver on his head with a phone.
The statement concluded that both the passenger and the driver had broken laws for seriously endangering public safety.
Police said on Friday, Nov. 2, 2018, a brawl between a passenger and a bus driver was the cause of the bus plunging off a bridge and killing more than a dozen people in southwestern China on Sunday.
Rescue teams said that at least 13 people died, while two remaining passengers are still unaccounted for following the accident.