Goran was a soldier in the Bosnian War and a member of the same fifteen man squad as Niko Bellic, Florian Cravic, Darko Brevic, Mijo, Dragan and Dmitar. During the mission, That Special Someone, Darko mentions that "Goran and his guys" had killed Darko's neighbours. This could have been a supporting factor to his eventual betrayal to the squad. These "guys" previously mentioned are most likely other members of the fifteen man squad. It is quite possible that Goran was the leader of the squad, which is why the other members followed him.