According to a FSA source the FSA opened fire on one of the pilots as he was descending using his parachute:
FSA source:
The dead pilot shown on video tried to fly his parachute into regime territory. Our fighters "shot him dead from a distance."
— Charles Lister (@Charles_Lister) November 24, 2015
This would be a war crime against a Russian pilot, which will without a doubt lead to an immense reaction from Russia against the FSA
Article 42 outlaws attacks on pilots and aircrews who are parachuting from an aircraft in distress. Once they landed in territory controlled by an adverse party, they must be given an opportunity to surrender before being attacked unless it is apparent that they are engaging in a hostile act or attempting to escape. Airborne troops who are parachuting from an aircraft, whether in distress or not, are not given the protection afforded by this Article and, therefore, may be attacked during their descent.
https://en.wikipedia.org/wiki/Protocol_I
