It was fighting inside of the van where the character was transported by bad guys (possibly character was a female, but I`m not sure). There were to guardians together with the main character in the van. One armed with smg, another with taser. During the fight they got to the position where smg-guy pointed his gun at the guy with the taser, and the taser in that guy’s hand touched the body of smgunner. The main character clicked the button on the taser causing the finger of the gunner to pull the trigger. Thus the head of the man with the taser was blown off.