Transcript for Bringing Otto Warmbier home from North Korea: Part 4
Reporter: After Otto Warmbier's trial, the north Koreans made sure the college student disappeared from sight. Nobody has seen or heard from Otto since March of 2016. Nobody. Reporter: In the beginning, father Fred Warmbier was also out of sight, part of a strategic silence requested by the Obama administration and the Warmbier's adviser. I gave them the same advice that I'd given to other families. They needed to be careful about things that they might say -- that might cause the north Koreans to react very angrily and badly. We were advised that it was important that you don't upset the north Koreans. Reporter: It was a tactical maneuver. One of many of both sides. Because as Otto's family and friends were agonizing back in Ohio, North Korea and the U.S. Were playing a game of geo-political chess, in which the 21-year-old was just a pawn. After they arrested Otto, four days later, there was a fourth nuclear test. North Korea saying they have successfully tested a hydrogen bomb. It takes weeks to prepare such a test so, they had in mind that they were going to do nuclear tests and there's going to be sanctions that follow. Reporter: What did Kim Jong-un get out of this if they throw Americans in prison? It would blunt any kind of heavy pressure from United States if you have American hostages. Like you -- maybe Americans will not conduct a military strike. Reporter: Like a bargaining chip? Yes, absolutely a bargaining chip. Usually, what the north Koreans have wanted is humanitarian assistance of some kind. Food, rice, in exchange. Reporter: Former New Mexico 2k3w governor bill Richardson now runs a foundation aimed at rescuing political prisoners. Reporter: But with Kim Jong-un, this new leader, we don't know what he wants. He stays silent. One of the very first things that I said to the Warmbier family was that the north Koreans will let Otto come home when they are done with him. When he is of no longer value to them. Reporter: Journalist Anna Fifield heads to that notorious hotel in Pyongyang, looking for answers, finding only frustration. I asked if I could see the place where he's alleged to have take down that poster. And there was just nothing. No news whatsoever coming out of the north Korean system. Reporter: Otto's father, Fred, works tirelessly to get his son back. We've been to Washington, D.C. Over a dozen times. We've met our senators, our congressmen, we've worked with governor Richardson. My organization worked with the family. Briefed them. Tried to get Otto out. Reporter: The response? North Koreans stiffed me. They never said yes. They never said no. Reporter: I was back in north Korea myself last September. Driving two hours south, we arrive at the demilitarized zone. So, here's the line. On the other side is south Korea? I met with the director general, high ranking official who told me Americans like Otto will be treated as prisoners of war. They began calling the Americans that they had in custody prisoners of war. All belts were off in terms of the -- the rules that they were required to follow. Reporter: Back in Ohio, the family was running out of patience. While Otto's friends prayed for his survival. If anyone can fight through it, it's Otto. He had the courage and bravery to do it. Thank you. Reporter: Then, in November, the U.S. Selected a new president. And the clash of the titans began. Both leaders are unpredictable. Right. Reporter: Both trump and Kim Jong-un. Right. Reporter: In February, the new president directed secretary of state Rex tillerson to take all appropriate measures to bring Otto home. As winter turned to spring, Kim Jong-un was making his own headlines, with more missile testing and accusations he killed his own half brother. Kim Jong-un is more frightening. He seems to be more brutal. He seems to be more reckless. He has anger management issues. He's acting very, very badly. I will tell you, he's acting very badly. Reporter: The new administration views its predecessors North Korea poll sill as something else to repeal and replace. The policy of strategic patience has ended. Reporter: By April, the Warmbier family has also changed it's approach and broken its silence. John Kerry was secretary of state at the time. Did he help you in any way? No. Absolutely not. Did anyone in the state department help you in any way? No. This sense of frustration and anger, I've heard it before, and I understand it. Reporter: This past April, we were in North Korea again, walking the super clean streets and hearing this chilling remark. Is it more dangerous now in terms of relationship between the U.S. And dprk than ever before? "I can say that the situation of the Korean peninsula is much more tense." Later that month, one week after parading its military might, the north Koreans detained another American -- Tony Kim. Detaining an American as he was leaving a teaching assignment there. Reporter: Was it an act of confidence or fear? Do you think they're more afraid of trump than they were of previous presidents? They might, just because the whole world thinks that Mr. Trump is more unpredictable. Tonight, I ordered a targeted mill stair strike. Reporter: And they've seen what happened with Syria, with the missile strike. So, I'm sure they are very nervous. Reporte Reporter: Then, a year after stone walling, negotiations for Otto's release begin. In may of this year, there were some of these talks. They were held in Oslo. And at these talks we now know was Joseph Yun. Reporter: Joseph Yun works for the state department, specializing in North Korea policy, and suddenly, he's making progress. Otto's friends envisioning their friend returning for fr his imprisonment in triumph. Coming home to the basement, giving him a big hug, and hearing his stories. Reporter: But within weeks, those hopes are dashed. Joseph Yun is summoned to an urgent meeting at the U.N. It was at that meeting on June 6th that the north Koreans disclosed that Otto Warmbier was in a coma. Now we know why the north Koreans stiffed me. Otto was in a coma and they didn't want anybody to know. Reporter: Secretary tillerson immediately dispatched Yun and his gulfstream 3 to the rogue nation with one order. Bring Otto home. Yun immediately insisted with the north Koreans he be released on humanitarian grounds. Reporter: And as Otto's loved ones were anxiously awaiting his arrival, the horror of his maltreatment suddenly was so real as he was brought off the plane, limp and unconscious. We were all very hopeful, no matter what people were saying. So, I don't think we really fully grasped how serious it was. Reporter: An exhausted father, wearing the same jacket Otto wore at his trial, was relieved his son was home, but brissefuling at the north Korean's claim that this was a humanitarian act. They wouldn't do this out of the kindness of their hearts. North Korea doesn't do anything out of the kindness of their hearts. I think the reason the north Koreans released him was because he was -- he looked like he was about to die. And they didn't want him to die in North Korea.
This transcript has been automatically generated and may not be 100% accurate.