Police examined nearly 2,300 hours of surveillance videos along the bus route to determine the cause of the accident which gripped the nation.
Originally, witnesses reported seeing the bus swerve to avoid another vehicle but distressing new footage has emerged showing the real cause of the accident: a fist fight between an irate passenger and the driver.
According to Wanzhou police, the fight started after a female passenger missed her stop and asked the driver to pull over immediately. All 15 people onboard are presumed dead.
The 42-year-old driver, surnamed Ran, told her to get off at an earlier stop.
The bus was retrieved from the river on Wednesday, and investigators were able to obtain the footage from the vehicle's surveillance system.
A search and rescue operation was launched on the Yangtze river near Chongqing in southwest China on October 28.
When the 43-year-old driver, also identified by his last name, Ran, refused, Liu hit him over he head with her cell phone.
The bus collided with an oncoming auto before smashing through barriers and into the Yangtze River on Sunday.
Thirteen bodies were found and two people were listed as missing.
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.
One poster on Weibo, Wanten888, said: "If we see any passenger quarrelling with bus driver, we shouldn't stay quiet!"
"The behaviour of both the passenger and driver has severely endangered the safety of all other passengers and has violated the law, ' police said, adding the tragedy served as an 'extremely painful lesson".