It was the owner of the car. You can see there’s no one in the car if you look closely. This was apparently a repo gone wrong - tow truck driver hooked up then got accosted by the owner and tried to get away. Dude got on the truck with a crowbar and smashed out the back window.
Source: http://www.presstelegram.com/general-news/20170822/wild-video-shows-compton-to-long-beach-car-repossession-gone-bad (via reddit.com/r/roadcam, always good if you like crazy car videos)
