I agree with Zorab 64 - The tail probably sheared through impact shock loading transmitted to it as the ac hit the ground possibly tail rotor first? But lets let the BOI sort out the detail and just say well done to the crew! Oh I think you will find it was pretty out of control and thats why the tail hit the ground not because someone was careless.
I've flown with both the pilots. Well done you 2, you know who you are!