Who knows really.
The only thing I can say for sure is what is present on that picture.
Dudes with UKR SF gear and UKR SF weapons.
Are they indeed UKR SF, or Russians dressed as UKR SF? No idea.
Are they UKR SF mistakenly arrested by UKR police? No idea.
Are they UKR ST arrested by Russian police? Considering the town would have been, assumedly, captured recently I would expect the police to, at least, be Military Police and not regular policemen.
Are they "Russian saboteurs"? No idea.
Who are the ones arresting them? No idea.
Is it a photoshoot? No idea, but that would not be a huge surprise. Lots of propaganda flying around.
If that's the case, whose side organized it? No idea.