It's not exactly clear what happened to make the guy in the white Suzuki punch the guy in the black Jetta. Neither car is damaged, so no accident seems to have occurred. Even so, Suzuki gives Jetta a pretty good sucker punch through the window... and ends up in cuffs two minutes later. That's pretty efficient!
This happened in Vancouver, BC, and while it's a little tricky to see what's going on through that rain-dappled dashcam, the maker of the video has included some handy callout text. It seems to be the happy accident of nearby cops and immobile traffic.
The 26-year old window opening-puncher was arrested and later released, and assault charges are pending.
It's satisfying to see the consequences of this act of assholery happen so rapidly. Way to go, chance accumulation of elements! Mighty fine work!