Did he really commit suicide after the investigation was over?
shareI guess no one answered your question but I guess he did. He killed himself because of guilt and the fact that he was now living in fear like a puppet no longer capable of free will. He killed the other guy knowing he was innocent, yet also out of both mercy and fear. And it was clearly against his principles and it obviously shook him.
You can see his shock at his beating, it was something he never thought would happen to him as a cop. And he never truly realized the oppressiveness and unethical nature of the regime he was living under until that moment. And in that moment, all his confidence and bravura went up like a smoke, he was simply a man living in fear and hunting/killing a man he knew to be innocent.
I also think he killed himself because he never realized he could be so weak and the postcard finally sunk in and he realized how true they all were. The realization that he took part in the hunt and capture of people he admired and knew were telling the truth, was what pushed him over the edge.