Sounds now like Icing caused an aerodynamic stall. Normally when a plane stalls (loses lift) the nose pitches down, causing the airspeed to increase to the point where the wing regains lift. It sounds like the plane went into a flat spin, as it was facing the opposite direction of the airport when it hit the ground. A cause for a flat spin following a stall is improper loading of a plane. If the center of gravity is too close, or behind (toward the tail) the center of lift, the plane cannot pitch forward in the event of a stall. Could it be that there was no-one in first class? People on the ground thought they heard the plane "sputtering"- if the plane was in a flat spin it would sound as if it was sputtering. Turbine engines don't sputter- either the fire is lit or it's not.