In November of that year he was appointed commander of the 67th Fighter-Bomber Squadron. During the night of Aug. 4, 1950, North Koreans had established a beachhead across the shallow Naktong River and their tanks, troops and artillery were moving steadily toward the nearby base at Taegu, the U.N. forces' primary airstrip. Early in the morning of Aug. 5, Sebille led a formation of F-51s, armed with 500-pound bombs and rockets, on a strike against the North Korean troops advancing toward Pusan. A T-6 Mosquito forward air controller directed them to attack forces near the small village of H'amchang. Sebille positioned himself for a medium-angle dive bomb run, planning to drop both of his 500 pound bombs on his first attack. Diving from about 5,000 feet, he held steady until about 2,500 feet. When the target passed under his nose, he punched the red bomb release button on his control stick, and then made a sharp pull-up to the left to stay away from his bomb blast. But only one of his bombs had released, and the heavy 500 pounds of unbalanced weight under his left wing perhaps contributed to his near miss on the first run.

Enemy machine guns were still firing as Sebille made the turn for a second bomb run, intending to pull the manual release handle to release the bomb. During his second attack, Sebille radioed that he was hit. His last words were garbled. He dove straight toward the armored carrier that was his target. He fired six rockets in salvo, but instead of pulling up at the 2,000 foot level, he continued to dive his airplane and the remaining 500-pound bomb straight into the target, crashing into the ground in a great ball of fire.

On Aug. 24, 1951, Sebille was posthumously awarded the Medal of Honor for his heroic sacrifice. He was the first of only four Air Force men awarded the medal during the Korean War. A special corner has been set aside at the Air Force Academy's Harmon Hall to commemorate the memory of his selfless heroism.