In the 1850s, he moved to Kansas with his brothers, part of his father's efforts to prevent Kansas from becoming a slave state. He participated in his father's famous raid on Harpers Ferry, Virginia (since 1863, West Virginia), where he was killed. The circumstances were that he emerged from the engine house at 10 AM on Monday the 17th, carrying a white flag, but was immediately shot, not by a soldier but by a townsperson. At 3 PM he was still able to fight. Lying on the ground and with no medical treatment, he lived on in great agony, his father preventing him from killing himself to end the pain, until about 3 AM on Wednesday the 19th, according to Edwin Coppock. According to his father, "our poor Watson lingered until Wednesday about noon of the 19th of October."