Otto Warmbier was a 21-year-old college student with a bright future when he signed on for a short tourist trip to North Korea in December 2015. Not until Tuesday was he finally flown home, gravely ill and reportedly in a coma.

He was arrested, tried on spurious charges and evidently subjected to horrendous mistreatment by North Korean authorities. This was outrageous behavior even by the standards of one of the world’s most vicious and isolated regimes. It should not go unpunished.

By his account, delivered at a scripted “news conference” weeks after his arrest, Warmbier attempted a foolish but harmless prank: trying (unsucessfully) to pilfer a propaganda poster from the hotel where he was staying. For this he was sentenced to 15 years hard labor following a one-hour trial. He had not been seen in public since then, and Swedish diplomats representing the United States in Pyongyang were denied access to him.

Now it appears that Warmbier may have been gravely ill for much or all of that time. His parents said that North Korea suddenly informed U.S. officials last week that the student was in a coma. He was said to have lost consciousness after contracting botulism and taking a sleeping pill — an account that strains credulity.

To its credit, the Trump administration arranged for Warmbier’s evacuation. Secretary of State Rex Tillerson refused to provide details, though one official said that the release had nothing to do with the latest bizarre excursion to Pyongyang by former NBA player Dennis Rodman. Not until he can be examined by medical specialists in the United States will it be clear what condition Warmbier is in and whether it can be remedied.

The harm done to an innocent student is the result of North Korea’s odious practice of seizing Americans to use as political pawns. Three other U.S. citizens are being held by the regime. President Trump should make their release a priority.

The United States should also move quickly to step up sanctions on the regime of Kim Jong Un, which has been racing to develop missiles that can reach the United States with a nuclear warhead. A new report by the research group C4ADS shows that by cracking down on a relatively small number of interlinked Chinese companies and individuals, the pressure on Pyongyang could be greatly increased. According to the Wall Street Journal, the Trump administration has asked China to act against some 10 entities; if Beijing does not respond promptly, the United States should act unilaterally.

Editorial by The Washington Post