A month ago, the media was celebrating civilians taking up arms, now they’re lamenting the inevitable result.
Mercinaries would be killed outright, but those casualties have no military markings - armbands or other identifiers.
If a civilian in Russian controlled territory is passing information to the Ukrainian forces, they may be tried as a spy and executed.
But I doubt that this was treatment of spies, saboteurs and franc-tireurs.
I suspect that this was revenge for the pounding the Ukrainians gave to the Russians when they were out of supplies and fuel. And shame and anger may unleash extreme brutality.