The actions of the truck which were bloody stupid... but I do detect a hint of "I'm going to drive barely quicker than the car in lane 1 just to pi55 you off" although there could have been further history to this further back:
https://uk.news.yahoo.com/road-rage-video-playlist-112350858.html
https://uk.news.yahoo.com/road-rage-video-playlist-112350858.html