A passenger furious that a driver went past her stop had started hitting him while he was driving, resulting in his swerving across the road and off a bridge, according to security footage from the bus. 
The bus fell 50m into the Yangtze River in Chongqing on Sunday, killing 13 people with two others still missing.
The dramatic footage captures the escalating fight within the bus as the woman strikes the driver who strikes back before he loses control and swerves across the road.
The bus hit a car travelling in the opposite direction and then the edge of the bridge, when the video stops abruptly .