Footage has emerged online of a BMW motorist threatening a school bus driver in a foul-mouthed tirade. br In his menacing rant the man tells the bus driver he will track him and his family down. br The clip taken on the yellow bus's dashcam on the morning of June 1 shows the vehicle driving children down a residential street in the US. br Parked cars line both sides of the road leaving no room for two-way traffic.