The Guard Post

The Guard Post GP 506 in South Korea is a 2008 Korean horror film written and directed by Kong Suchang.

Noh arrives at GP 506 about an hour later. On the way to the office, he passes a boiler room that has words written in blood on the wall, which says Kill all of them. He is brought to the recreation room where the bodies were found, and watches in shock at the amount of blood splattered around the room.In the present, Noh checks the guard posts records and notices that someone has been controlling the weapons lately. All personal weapons were kept in the armory and not in the barracks, which was unusual. One of the soldiers reports to Noh, informing him that they have found another survivor, inside the generator room. ........

Source: Wikipedia