Updated at 3:50 p.m. ET
Otto Warmbier, the U.S. student freed this week after more than a year in North Korean detention, sustained "extensive loss of tissue" in all parts of his brain, his doctors say.
Warmbier has remained in a coma since his return, suspended in a state "best described as unresponsive wakefulness," Daniel Kanter, head of the neurocritical care program at University of Cincinnati Health, told reporters at a news conference Thursday.
Kanter and his colleagues say they've found no evidence that Warmbier, who has demonstrated no awareness of his surroundings, suffered from the effects of botulism — a finding that appears to contradict the explanation offered by his North Korean captors. Authorities there have said Warmbier fell into a coma after contracting botulism and taking a sleeping pill.
Instead, the doctors told reporters that the more likely cause of Warmbier's condition is cardiopulmonary arrest. Their tests also did not reveal any signs of physical trauma to Warmbier, such as "acute or healing fractures."
Earlier Thursday his father, Fred Warmbier, said that North Korea's regime had "brutalized and terrorized" his son for more than a year, and that he's happy Otto Warmbier is now home. He said his son will now get medical care that he was denied in North Korea.
As he spoke to the media Thursday, Fred Warmbier also said he was glad to be wearing the same jacket his son had worn during his court appearance in North Korea.
"I'm proud of Otto, and the courage he showed by going to North Korea," Warmbier said, "and having that adventurous side to him ... so the fact that he was taken and treated this way is horrible, and it's tough to process. But we're tremendously proud of him. So we're looking to the future."
"We don't believe anything that they say," Fred Warmbier said, describing North Korea as a pariah state. He said his son had become "fodder" for the regime, after being lured into visiting the country by a Chinese travel company that promised its customers were never detained while on a tour in the isolated nation.
Otto Warmbier, 22, had been sentenced by a North Korean court to 15 years of hard labor in prison after he was accused of trying to steal a propaganda banner at his Pyongyang hotel. But it emerged as he traveled back home that Warmbier, a University of Virginia student, was in a coma.
"Disbelief," is how Warmbier described his immediate reaction to being told last Tuesday that his son is in a coma. "I don't know what being in shock is," he said, "but I'm pretty sure I was."
In recent months, Warmbier said, he and his wife, Cindy, had decided to take a more public stance in calling for their son's release, after months of following advice that they should try not to antagonize or offend leaders in North Korea.
When asked whether he believes the Obama administration could have done more to secure Warmbier's release, he replied, "I think the results speak for themselves."
He said that he had spoken to President Trump last night, describing the call as gracious.