This is the best description that I could find about this video:
When both sides use tanks based on the Soviet T-72 Model, it's common to confuse friendly and enemy tanks. Hence why the Russians paint big white letter Z's on their armour.

In his video:

1. A group of Ukrainian infantryman casually waits on a highway believing the approaching tank to be friendly.

2. At a distance of 20 metres the Russian Tank crew opens fire point blank into the group of Ukrainian infantry after noticing the soldiers in front of them are wearing Ukrainian patches.