There was a group of people all dressed in white in a big room…also white. There was one door and a little box on the wall that contained a gun. Someone else had the key i believe. I don;t know what the experiment was about i do know that they start dying or even killing each other. I also remeber vaguely that once in a while somebody would come in the room and kill or drag somebody out.
could they not be wearing white?
Maybe The Belko Experiment (2016)?
killing room (2009)?
do you remember if it was in english? could it be a tv show episode? i am struggling but looking very hard.