Need Help Interpreting Preliminary NTSB Turbine Engine Inspection Post Fatal Rotorcraft Accident

While on final instrument approach, the Eurocopter EC-135 (Equipped with two Pratt & Whitney Canada, PW206B2 engines) suddenly rapidly descended and impacted terrain a mile from the threshold of the ILS runway it was on final for. The only occupant on board (the pilot) was fatally injured and pronounced dead on scene. The NTSB released their preliminary report and I am trying to interpret the mechanical findings in the document. I understand this is a very basic preliminary report, but as the final report is not due for 18 more months, I was hoping to try and comprehend the information currently available.

After reading the entire document, nothing jumped out at me as an obvious cause for the crash. The NTSB reported no radio traffic from the pilot indicating distress, and radar data depicts relatively normal flight ops until the aircraft made a sudden rapid decent and turn to the right off the glidescope. Everything I read regarding the mechanical findings seemed like normal damage from a severe impact such as the one sustained. The only damage reported that did not sound impact related was damage discovered in the power turbines of both engines. The report states "The left engine power turbine was removed and the drive shaft exhibited torsional deformation and fractures. In addition, the power turbine wheel exhibited rotational scoring." The exact same was listed for the right engine in the paragraph that followed.

My question is if anyone knows what can cause this type of damage in a turbine? Maybe this is a normal discovery for a high speed impact, but it jumped out at me as something that would not be impact related. I tried doing research on-line and could not find any answers.

Disclaimer: I am not a pilot or mechanic so my understanding of helicopter maintenance and mechanics is extremely limited. That being said I have experience working as an Air Medical Communications Specialist (Dispatcher) so I at least have a basic understanding of rotor-wing aviation in general. I will be upfront with my stake in this game. A close friend and former co-worker was the pilot of a fatal accident that occurred last week. If you have ever lost someone you are close with in unexpected circumstances, you will understand the compelling urge to answer some of the lingering questions.

Thanks for any help...