Sad news, especially at Christmas.
I don't speculate about causes of accidents and I'm sure many will fill the gap over the next few days.
I do however have concerns about CL aircraft take-off accidents.
There have been enough to catch my attention including a fatal at Birminghm (BHX) a couple of years ago and one at Moscow last year(?)
Low temps seem to have been a factor in those. Regardless of the final outcome of investigations into this tragedy, could a positive from this thread be to spread the word to CL pilots about contamination from frost or ice, and the effect it has been shown to have on this model?
Hope the injured make full recoveries.
Sir George Cayley