An individual civilian walking down the street in what is reportedly Kyiv spots a man placing an IR beacon on a fence to signal future airstrikes for the Russians.

This is what you're looking at. The first man the person filming spots is a Russian Saboteur. A common tactic the Russians have been using is placing IR beacons on potential targets for airstrikes and artillery strikes. The second man you see is a random civilian walking down the street. He spots the saboteur affixing the IR beacon to the intended target, and immediately jumps to action by himself.

Here's the impressive thing. The civilian doesn't know the saboteur's capability. There's a strong chance that the saboteur could be a member of a Spetsnaz unit with extensive training in hand to hand combat. The Ukrainian is just a civilian from the looks of things, but regardless he jumps to action and detains the saboteur all by himself with absolutely no help or anyone around him to come to his immediate aid.