During in the Korean War, approximately 25,000 to 35,000 people were killed in the Yeonggwang area due to diverse causes. In this paper, I argue that “the crowd theory” is a relevant theoretical frame to explain massacres in the area. That is, due to local conditions, residents became part of an armed crowd, as well as act as part of the crowd, killing massive numbers of civilians. The first condition contributing to the crowd formation is the absence of control by political authorities. The second factor is the geographical characteristics of the Yeonggwang area such as sea route to the North Korea and retreat area of leftists. The third factor is the frequency of armed conflicts between the leftists and the rightist military and police. The fourth factor is that the Yeonggwang area was not recaptured area for long. Because of these factors, people became part of an armed crowd, and huge civilian massacre broke out.