U.S. Army 19th Infantry troops had been in action along the Kum River through 16 July 1950. They intended to disengage but their retreat was blocked by Communist forces.
Quotes below are from the wikipedia article:
"U.S. troops from the 19th Infantry, desperate to move around the roadblock to obtain supplies and care for wounded, began moving through the surrounding hills. One tank was able to make it through the roadblock to evacuate the 19th Infantry's wounded commander, but by 19:00 commanders ordered the regiment to move its wounded along the ridges to the east of the roadblock."
"...At 21:00, about 100 men of the 19th Infantry moved into the hills to the east of the town. They carried with them about 30 wounded, including several litter-bound patients too seriously wounded to walk. Some of the group of 100 were ordered to carry these men, but many of them separated from the group in the mountains. By the time they reached the top of the mountain, officers decided some of the seriously wounded could not be carried any further, as their carriers were exhausted.
"The regimental medical officer, Captain Linton J. Buttrey, and Chaplain [Franciscan Roman Catholic priest] Herman G. Felhoelter remained behind with the wounded, intending to move them when another group of troops came through who could carry them."
The chaplain urged the medical officer to escape. Buttrey was wounded but survived.
"...[O]bservers from the 19th Infantry's regimental Headquarters and Headquarters Company watched through binoculars from a distance as a patrol of young-looking and possibly untrained North Korean troops approached the site of the wounded. The troops were armed with Soviet-made rifles and PPSh-41 "burp guns". As Felhoelter knelt to pray over the wounded U.S. soldiers, the North Korean troops shot him in the head and back. They then proceeded to shoot and kill all of the 30 critically wounded soldiers with their automatic weapons before withdrawing into the wilderness."
Father Felhoelter had received the Bronze Star as a chaplain in World War II. He was awarded the Distinguished Service Cross posthumously.