Pure speculation here but, it appears the pilot either lost an engine on takeoff or tried to bank the plane without sufficient airspeed. I would bet on the latter because of the attitude of the aircraft at the beginning of this video.
I retract my comment regarding the pilot banking without sufficient air speed after seeing the video provided by zipper. From that video it appears that a mechanical issue caused a loss of airspeed or flight surface control.
Stall/Spin out of a turn. Could have been instigated by a critical engine out.