This rather, robotic-voiced discussion seems a reasonable review of the facts surrounding this dark page in Korean War history.
In October 1950, North Korea (DPRK) claims that, during the retreat of the DPRK’s Korean Peoples Army from Hwanghae Province, Southern Korea (ROK) military forces (authorized by U.S. military) killed ~35,000 people.
Other sources dispute the death toll and accuse Korean right-wing security police and communists of the killings.
North Korea claims the event (referred to as the Sinchon Massacre) resulted in the deaths of ~1/4 of the population of Sinchon over the course of 52 days before a counterattack by Chinese and North Korean forces.
Here is what North Koreans are told today at the Sinchon Museum of American War Atrocities.
The Sinchon massacre “cannot be understood simply as killings between the left and the right,” South Korean historian Han Sung Hoon alleges. It must be understood three-dimensionally, as the explosive result of the contradictions emanating from the colonial period after liberation, combined with the division and establishment of two separate states in the North and South, and eventual war, which exacerbated the internal problems of class, hierarchy, and religion.”