The white truck on the right is approaching someone, who just happened to have a camera aimed at other truck & train?
There are an increasing numbers of videos like this online. A driver gets high-centered on the rail crossing. Other drivers stop to help. Some time later a freight train comes along and bam!
This train was going relatively slow compared to other ones that smash the truck and drag the carcass and contents a mile and half down the track.
They're not just filming for kicks or clicks. They're often doing it for law enforcement as well as the insurance company. I suspect many drivers are filming it to justify why they're late with their own delivery after stopping to try to help.
I’ve seen similar videos where the driver had time to disconnect the trailer in order to save the tractor.
This clip starts with the semi already on tracks and Train already there…immediately pushed over. The filmer likely already was aimed at it when the semi moved into the tracks. People have these damned phones and now dashcams everywhere, it’s not shocking someone with stopped traffic is filming what looks curious…he just got “lucky” that it was that dramatic indeed.