Apparently, the units in the area of those Bucha atrocities included Chechen National Guard (Rosgvardia), and the Russian 76th and 98th Airborne (VDV).
I suspect that the Chechens were the ones who committed atrocities. After all, many Russians, it seems are not very enthusiastic about fighting and killed other East Slavs, so they may not be keen on committing war crimes on civilians.