The fatal shooting of a South Korean tourist near the Mount Geumgang resort by a North Korean soldier on July 10 should never have happened. In the past, whenever a South Korean strayed into a restricted area, the visitor would be detained and then released when identified as a member of a tour group.

North Korea’s explanation so far has only fueled speculation that the shooting was premeditated. For example, the North claims warning shots were fired when the victim, a 53-year-old housewife, ignored an order to halt and tried to flee. But a South Korean near ...