It was in a left turn, so possible banked too far and stalled. Lear jets require a high level of proficiency as you can get behind the power curve very quickly. It’s a very unforgiving plane. A few years ago another air ambulance Lear jet crashed in San Diego after cancelling IFR while circling to land. If you want to hear the last words of the pilot google N880Z atc last words. Warning...not for the faint of heart.
I wonder how many hours the flight crew had been on duty in the previous 2 or three days and if fatigue played a factor.