The king remembered vividly what happened to the only living soldier and witness who knew about the village boy, who happened to awaken the forbidden bloodline.
The soldier kept under the roof of his castle, slept, and did not wake up the next day. Of course, many people slept and did not wake up the next day, but the timing of the soldier's death was so out of place. The king was frightened by the unusual circumstances surrounding the soldier's demise.
From the king's perspective, it seemed as if the witness had been intentionally eliminated. Erasing witnesses was not uncommon and did not scare the king. He had given such orders before.