I have two thoughts on what may have happened.
First: Say the aircraft is laden with ice from the approach. Control extension (flaps) caused a section of ice to come off, upsetting the balance, sending the plane into a spin. On high-wing airplanes, ice will still build up behind the boots. The ATR was famous for it. Remember the Eagle ATR that crashed in Roselawn IN while on approach to ORD? Same style of airplane. And, oddly, the tail section was the only section left intact in that one as well. Eerily similar.
Second: The NTSB released a statment that they were "looking into the possibility of structural failure." Say the main wing spar failed, but the wing did not depart the aircraft. that would send it into a spin as well.
Lets keep in mind the airplane was facing away from the airport. I find thawt to be strangest of all. That tells me the airplane went into a spin and fell straight down onto her belly.