At first glance, it seems the U.S. can't do anything about Otto Warmbier's treatment by North Korea.

Three other Americans are detained there, and officials don't want to jeopardize their safety. Plus, the unpredictable regime in North Korea – the same regime that "decided on a whim" to arrest Otto, as one Cincinnati professor put it – has nuclear weapons. And the U.S. doesn't want to provoke the use of those missiles on ally South Korea.

“It’s a matter of leverage. And we’ve got fairly minimal leverage,” said Richard Harknett, head of the University of Cincinnati’s political science department. "This is the most sanctioned country, practically, in the world. There's not much else we can do."

But some say Americans, particularly those in government, can do more.

They can speak out publicly about North Korea, instead of staying quiet for fear of offending. They can put public pressure on North Korea's ally, China. They can change the long-term policy, under both Republican and Democratic administrations, of silence.

They can be more aggressive to bring others home. To prevent another Otto.

That's the approach the Warmbiers eventually took. After a year of remaining silent, they began appearing on prime-time news shows, demanding that more be done to bring home their son. That may have put more pressure on both Washington and Pyongyang, but complaints from high-ranking officials would have worked better, said Phil Robertson of Human Rights Watch. Governments, he noted, respond to "pressure, embarrassment and exposure."

For years, the State Department has worked privately to negotiate the release of Americans detained in Korea, often working through an intermediary such as Sweden. Government officials in the know are told not to say anything publicly that might provoke North Korean retaliation against U.S. citizens.

Eventually, the approach usually works.

In Otto's case, it didn't. His situation represents the worst outcome for any American detained by North Korea.

Otto, a Wyoming, Ohio, native, was a 21-year-old University of Virgina student when he visited North Korea with a tour group in late 2015. He was detained as the group was preparing to leave the country in early 2016 and charged with engaging in anti-state activity.

He was held for a year and a half. His family got one letter from him, dated March 2, 2016, and then – nothing.

"We tried to stay low," Otto's dad, Fred Warmbier, told reporters Thursday morning. "We were advised that it was important that, 'You don't upset the North Koreans.' We followed that logic."

But nothing happened.

So, Fred and his wife decided to start talking.

Much remains unknown about what happened to Otto in North Korea, but he reportedly has been in a coma for more than a year. Brain scans show severe damage. Cincinnati doctors on Thursday described his condition as "unresponsive wakefulness."

The Warmbiers broke the tradition of silence when, in April, they started speaking publicly about his imprisonment. They gave interviews to Fox News Channel's Tucker Carlson and The Washington Post, among others.

That sort of thing goes against official State Department advice. But now that everyone knows about Otto's condition, few on Capitol Hill are blaming the Warmbiers.

A State Department official, who declined to be identified by name, would say only that department officials have "seen reports about Mr. Warmbier’s health. Out of respect for the privacy of Mr. Warmbier and his family, we have no further comment."

There are the three other American detainees to worry about, after all.

Others, though, are starting to question the protocol of silence.

"North Korea seems to have been holding onto him quietly, hoping his situation improves so that they can get back to using him as a political bargaining chip," saidRobertson, deputy Asia director for Human Rights Watch.

Otto's condition – and the fact no one knew about it for a year – shows the limitations of the State Department approach, Robertson said. The department acknowledges its limits in its official stance on North Korea. "We can’t guarantee that we can get people back, so we encourage you not to go," spokeswoman Heather Nauert told reporters Thursday.

Instead, members of Congress, representatives to the United Nations and governors should put public pressure on North Korea to release more information on Otto's situation, Robertson said.

“North Korea, whatever we say, they’re going to pay attention to what is happening," he said. "When they don’t see anything happen, they think, 'OK, we can delay, we can bargain, whatever, because we don’t see any big reaction.'"

North Korea should be “universally condemned” for how it treated Otto, said Sen. Rob Portman, a Republican from Terrace Park.

Portman's stance long has been to be tough on North Korea regarding the country’s nuclear testing and its “inability to live within the rules that the rest of the international community has established."

Now, he plans to get more aggressive on the country's treatment of detainees.

In particular, he wants China to toughen up. The way Otto was treated is inexcusable, he said, and China has to make it clear it won't do business with a country that acts like that.

In the past year and a half, Portman grew close to the Warmbiers, he said. He was at the airport with them Tuesday night when Otto landed.

“No family should have to go through what they’ve gone through,” he said. “They’re remarkably strong.

“I’m hopeful that what happened to Otto will embolden members of the House and Senate – and, most importantly, the international community – to increase pressure on this pariah country.”

Nations and international rights groups should pressure North Korea to accept an investigation into its treatment of Otto as a possible violation of the Geneva Convention, former New Mexico Gov. Bill Richardson said. Richardson, who served as U.S. ambassador to the United Nations under President Bill Clinton, now serves as a negotiator for detainees in countries hostile to the U.S. and had sought to secure Otto’s release.

The U.S. should also press for additional international sanctions on North Korea, Richardson said. The U.N. Security Council this month expanded sanctions on North Korea after its recent nuclear missile tests, but China has opposed more stringent efforts, such as an oil embargo.

Perhaps holding up China’s ally as a human-rights abuser, a place where a young man’s life was destroyed, might change the country’s mind. The ultimate hope: that pressure on North Korea could result in the release of the other three Americans held in that country.

“This a real opportunity to say to the Chinese, ‘Look at these human rights violations. Look what they did to this young man,’ ” Richardson said. “This is one of the worst violations, the most egregious treatment of human rights that I’ve seen.”