It looks to me like the brakes on the truck failed. You can see him pull over into the parking space close to the edge of the frame but he doesn't slow down much. He's definitely not accelerating. There's also someone running from that direction shortly before the video ends.

Still, I'm completely baffled by the lack of reaction from everyone else there... Maybe the civilians are afraid of getting involved.

That's just me armchairing from afar, but I can imagen that life in the occupied parts of Ukraine is one with a lot of fear of the military and also fear by the military. There has to be constant fear in every layer of the military of getting targeted by partisans. Also I can only imagine the occupants viewing the people there as being "only" Ukrainians, despite the Kremlin claiming they are Russians. The see them not as equals. So driving carefully through this city with potentially hostile people you view as beneath you my be, in the mind of a russian footsoldier, dangerous. And it wouldn't matter anyway because those people aren't real Russians anyway.

And all the people acting like nothing happened probably have fear to get involved in anything to do with the military. They know where you live and they can pay you a visit at any moment if they think you called the police on them.

As I said, that's just my opinion I formed watching this insane war playing out in various forms of media.