WYOMING, Ohio — Wearing the jacket his son Otto Warmbier wore at the sham trial that ended with his imprisonment in North Korea, Fred Warmbier denounced the “pariah” regime that had brutalized his son, and fought back tears Thursday as he remembered kneeling to hug him when he was returned to the United States in a coma.

“The fact that he was taken and treated this way is horrible,” Fred Warmbier said. “They’re brutal and they’re terroristic. We see the results of their actions, with Otto.”

Otto Warmbier is in stable condition but has suffered a severe neurological injury, Kelly Martin of the University of Cincinnati Medical Center told reporters at the news conference Thursday.

Warmbier, 22, a student at the University of Virginia, had been detained in North Korea for 17 months and had no contact with the outside world for much of that time. He had been on a five-day tourist trip on his way to a study-abroad trip to Hong Kong when, on his last night there, he apparently tried to remove a large propaganda sign. He was charged with “hostile acts against the state” and, after the trial, sentenced to 15 years of hard labor.

Earlier this month, U.S. officials learned that he had been in a coma for more than a year, news that triggered an onslaught of diplomatic pressure for his release. He was medically evacuated and reunited with his family Tuesday.

Warmbier has extensive loss of brain tissue and is in a state of unresponsive wakefulness, UC Health doctors said Thursday afternoon.

Doctors said they don’t know what caused the brain damage. When asked whether it could be the result of beating or other violence while in prison, they said that Warmbier did not show any obvious indications of trauma, nor evidence of either acute or healing fractures.

Rather, Daniel Kanter, medical director of the neuroscience intensive care unit at UC Medical Center said, the pattern of brain injury they see on magnetic resonance imaging results appeared consistent with a cardiopulmonary arrest, with damage to brain tissue caused by lack of blood flow to the brain.

The doctors are not aware of anything from his previous medical history, before his time in North Korea, that might cause cardiopulmonary arrest. One of the more common causes of cardiopulmonary arrest is respiratory arrest, said Jordan Bonomo, neurointensivist at UC Gardner Neuroscience Institute. That cessation of breathing could be triggered by several things, including intoxication or a traumatic injury.

It is possible to have respiratory arrest caused by an overdose of medication, intentional or otherwise, he said.

Warmbier has undergone a battery of tests since his arrival at the University of Cincinnati Medical Center Tuesday night. Throughout that time, his family has been at his bedside, doctors said.

They declined to discuss his prognosis or speculate about the future, at the family’s request.

They said he has spontaneous eye-opening and blinking, but shows no signs of understanding language or awareness of his surroundings. He has not spoken, nor has he engaged in any purposeful movement, Kanter said.

“We don’t feel he has any conscious awareness,” Foreman said.

They have had no direct contact with North Korean medical authorities, Kanter said, but Warmbier arrived with two brain scans dated April and July 2016. They don’t have any way to verify those dates, but the damage to the brain is consistent with the deterioration they see from those previous scans, he said. After the tissue is damaged initially by insufficient blood flow — which they think probably happened before that initial scan — the body tries to remove the damaged tissue. “That’s what we’re seeing is this removal.”

Warmbier’s ordeal could escalate tensions between the United States and North Korea. But on Thursday, Fred Warmbier told of the personal toll it has taken, and the profound sense of relief that he and his family feel at no longer having to think about potential reaction from North Korean officials to everything from their words to the blue and white ribbons his neighbors tied to trees in this small city near Cincinnati to show their support for the family.

He spoke at Wyoming High School, where Otto Warmbier was salutatorian in 2013.

“This is a place where Otto experienced some of the best moments of his young life,” Fred Warmbier said, with two of his son’s former teachers at his side. His wife, Cindy Warmbier, was with their son at the hospital, he said, as she has been since he arrived home Tuesday night.

He thanked the people who supported the family through the 18-month ordeal with their thoughts and prayers, and those who helped get his son home, especially Trump administration officials.

About 10 p.m. Wednesday, President Donald Trump called him, he said, asking how Otto was doing and urging him to take care of himself. “It was gracious,” he said. “It was nice.” He said the president told him that Secretary of State Rex Tillerson and others had worked hard to free his son, and that he was sorry about his condition.

On Thursday, North Korea’s state-run news agency said that a court had allowed Warmbier to return home “on humanitarian grounds.”

Warmbier said he thinks the State Department was pretty tough with them. “They did not do this out of the kindness of their hearts.”

Asked whether he felt that the Obama administration had not done enough to help, Warmbier said, “I think the results speak for themselves.”

He said he wanted to highlight the bittersweet relief that his son is now home in the arms of those who love him — and anger that he was so brutally treated for so long.

The family went 15 months without a word from their son, he said, only to find out a week ago that he was in a coma all of that time. Even if people believe the North Koreans’ explanation — “and we don’t,” he said — “there is no excuse for any civilized nation” to have kept his condition a secret and denied him medical care for so long.

When news broke Tuesday morning that Otto Warmbier would be coming home, after a year and a half of detention in North Korea, blue and white ribbons began appearing on trees in his home town. By noon, the entire stretch of the main street, shaded by branches arching overhead, had ribbons on every tree and every utility pole, hundreds and hundreds of them.

“We’re all just focused now on providing privacy and any assistance we can to the family,” City Manager Tetley said. “We’re continuing to pray. Everyone wants so desperately for this situation to turn out well.”