It looks to me like the first guy noticed the aft opposite lashing was still attached so his oppo went to release it. It then looks like the pilot tried to apply a take off force slightly lifting the rear of the skid which applied a forward force. Then when the second guy actually released it the helo lurched forward and the pilot realising he would hit the structure hauled back on the stick causing a tail down pitch which caused the tail rotor to strike the deck shearing the tail rotor drive. Then it simply spun due to lack of anti torque tail rotor force and very luckilly came to rest.
Not very good piloting skills when you consider he tried to take off with someone to the rear of the aircraft and extremely lucky not to kill the deck crew or go over the side himself.
S