Nakajima was an officer who worked in the Gotham City Police Department.
Harvey Bullock and Jim Gordon arrive at the factory where Professor Pyg was last seen. When they enter the factory, they find Nakajima sitting on a chair, alive, with a pig's head over his own. As they remove the mask, it pulls a pin out of a grenade that Pyg put in his stomach. Jim and Harvey try to run to safety and Nakajima explodes.