I was sitting outside my hooch, at Marble Mountain, late 1968 or early 69. I had a clear view down towards the showers and out- houses ( the polite name ). A Marine was going to the showers, wearing only a towel, and stopped off at the out-house to do his business. What he was doing was fairly clear since the door and upper half of the walls were just screens. I could not hear what happened, but from his actions I can guess. He lifted the lid, turned and ran through the door, fell and did a high crawl at high speed. He had gotten about twenty feet from the door when green smoke billowed out of the out-house causing myself, and others with me, to nearly die laughing. Tough humor for tough times.
I can only assume that someone booby trapped the lid with a smoke grenade, and hearing the sound of the pin coming out or the spoon coming off, encouraged the Marine to leave most riky tik.