You can see the pieces of "tail boom" fall at the beginning of video.

Russian pilots have recently shared a new video of combat operations of their helicopters in Ukraine. The Russian Ka-52 Alligator attack helicopter demonstrated the wonders of survivability during its combat mission.

Having lost the tail boom of their helicopter, the crew managed to continue the flight and come back to the airfield.

Update found:  
When the outboard fuel tanks were jettisoned, they were blown back, and as a result, one of the tanks broke the tail boom of the helicopter.

Thought this was a good comment found:

Co-axial rotors. Contra-rotating twin rotors. Single rotor helicopters only need the tail rotor to counter the spin induced on the airframe as a result of having a single rotor. The KA-52 doesn't have a tail rotor.