And how does the Trump administration respond?
Tillerson says the State Department secured Warmbier's release at President Donald Trump's direction.
Yun and an American delegation traveled to Pyongyang on June 12 and demanded to visit Warmbier and his release on humanitarian grounds. His parents say he's on a Medivac flight on his way home. Let me reiterate this: "We strongly, strongly suggest that Americans do not go to North Korea".
According to the New York Times, American officials suspect that Warmbier's condition could be the result of brutality he may have suffered at the hands of prison guards, given that the North Korean regime has a history of mistreating prisoners.
A small group of family friends was nearby to celebrate Warmbier's arrival, cheering and holding signs that read "Pray for Otto" and "Welcome home Otto". Warmbier was sentenced to 15 years hard labor in 2016 for allegedly committing "hostile acts" against the North Korean regime. The U.S. does not have diplomatic relations with the reclusive country and works through Sweden to deal with North Korean officials.
The star has visited the North at least four times before, most recently in 2014 when he attracted a deluge of criticism after being filmed singing happy birthday to his "friend for life", leader Kim.
Following the May meeting in Oslo, North Korea urgently requested another meeting, which took place last week between the US envoy on North Korea, Joseph Yun, and the North's ambassador at the U.N.in NY.
Yun then met last week with the North Korean ambassador at the U.N.in NY.
Secretary of State Rex Tillerson announced that Warmbier had been freed. While it is a secular school - North Korea keeps a tight grip on information about religion - the university chiefly employs Christian staff.
Tillerson, at a U.S. Senate hearing on Tuesday, declined to comment on Warmbier's condition. The North Koreans "were informed that the airplane would land, American and medical officials would get out".
Senate judiciary probe may review obstruction of justice
Kasowitz heads the group despite his lack of deep experience in Washington or in criminal defense. That lack of formal notification wouldn't be unusual in the early stages of an investigation.
Warmbier, 22, returned to the United States in a coma. Yun and two physicians flew to Pyongyang and visited Warmbier on Monday.
Warmbier's release came during a visit to North Korea by former National Basketball Association star Dennis Rodman, one of few people to have met both North Korean leader Kim Jong Un and President Donald Trump, who was Rodman's boss on "Celebrity Apprentice". Tensions between the United States and North Korea have been high since Donald Trump took office in January 2017.
North Korean state-run media said early previous year that Warmbier was arrested for what they described as "a hostile act" against the regime.
According to the Washington Post, North Korean officials contacted American counterparts last week to tell them Warmbier was in a coma.
During his 18-month incarceration, the Warmbiers heard from Otto only once, through a letter on March 2, 2016.
There was no immediate confirmation from USA officials of North Korea's description of his illness - including whether he was stricken with botulism, a potentially fatal disease that is caused by a toxin but is not usually associated with loss of consciousness.
While traveling in Tokyo, Thomas Shannon Jr., the US undersecretary of state for political affairs, said Rodman was not acting in any official capacity. It wasn't immediately clear whether his release was connected to Rodman's visit.
A North Korean foreign ministry official, requesting anonymity because no formal North Korean statement had been released, said only that Warmbier was released and left the country Tuesday. President Teresa Sullivan said in a statement Tuesday.
"We received a call from Cindy and Fred Warmbier early today to update us on Otto's condition".
Sen. Rob Portman, R-Ohio, confirmed the release but did not comment on Warmbier's health. Shortly after Warmbier's sentencing, Kim Dong-chul, was arrested on accusations of espionage, and has been held ever since.
North Korea's first private university, PUST was founded and remains operated by actors outside the country, mostly Evangelical Christian organizations.