update: Apologies. The vid is from July. I picked it from Twitter and thought it was today's incident.
The Ukraine is panting to destroy itself. Let it. According to the poster of the vid, the Ukrainian army started firing at crowds gathered in the streets of Mariupol.
How can someone start firing at people who are not armed ? All they have with them are their cellphones.
A word of caution: This vid might be from earlier encounters. I just can't trust anything I see or read these days as the Gospel truth. Everybody has their own agenda and their own brand of propaganda.