It doesn't need to move sideways, if the BA vehicle is moving uncontrolled (with the driver incapacitated), then it could conceivably have strayed into the path of the Ops vehicle in an unpredictable manner. Or it might not have. But you don't know, and you're jumping to a conclusion; A picture of the scene following an accident rarely paints a clear picture of the events leading up to it... Let the police do their job and investigate.