WYOMING, Ohio (CBSNewYork/AP) — An American college student has died after being imprisoned in North Korea and returned to his home state of Ohio in a coma.

The family of Otto Warmbier said he was pronounced dead at 2:20 p.m. Monday.

“It would be easy at a moment like this to focus on all that we lost – future time that won’t be spent with a warm, engaging, brilliant young man whose curiosity and enthusiasm for life knew no bounds. But we choose to focus on the time we were given to be with this remarkable person,” Warmbier’s parents, Fred and Cindy Warmbier, said in a statement. “You can tell from the outpouring of emotion from the communities that he touched – Wyoming, Ohio and the University of Virginia to name just two – that the love for Otto went well beyond his immediate family.”

As of this past Thursday, doctors had said Warbier had been in ‘a state of unresponsive wakefulness.’ Doctors said his exam showed a ‘spastic quadriparesis,’ this means he has “profound weakness in contraction of the muscles in his arms and legs.”

A brain scan showed extensive loss of tissue in all regions of the brain, but doctors said there was no “certain or verifiable knowledge of the cause or circumstances of his neurological injury.”

Medical officials said that condition is often caused by cardiopulmonary arrest that results in an inadequate supply of blood to the brain.

Based on analysis of pictures provided by North Korea, doctors at the University of Cincinnati Medical Center believe the injury occurred sometime in the weeks prior to April 2016.

His father, Fred Warmbier, said he does not believe North Korea’s explanation that the coma resulted from botulism and a sleeping pill. He said there was no reason for North Korea to keep his 22-year-old son’s condition a secret and deny him top medical care.

North Korea presented Otto Warmbier before the media on Feb. 29, 2016, at an event where he tearfully confessed that he tried to steal a propaganda banner while visiting the country. He was last seen publicly that March, when he was sentenced for subversion to 15 years in prison with hard labor.

Fred Warmbier said last week that he doesn’t know why North Korea released his son but that the country doesn’t do anything out of “the kindness of their hearts.” He called on the country to release three other Americans currently held there.

“There’s no excuse for the way the North Koreans treated our son,” he said.

Warmbier also accused North Korea of luring Americans to the country with a Chinese tour company making the false promise they will never be detained.

Fred Warmbier told Fox News’ Tucker Carlson on this past Wednesday that Otto was “terrorized and brutalized” during his 17-month detention and has been in a coma for more than a year.

“The day after he was sentenced, he went into a coma,” the father said in an interview scheduled to air Thursday night. He said he and his wife, Cindy, only learned of their son’s condition last week.

The University of Virginia student was medically evacuated from North Korea and arrived in Cincinnati late Tuesday. He was then taken by ambulance to the University of Cincinnati Medical Center.

In its first official comment since Warmbier was returned home, North Korea said it released him for humanitarian reasons. The state-run Korean Central News Agency on Thursday did not comment on his medical condition.

Bill Richardson, a former U.S. ambassador to the United Nations, called for an investigation into what happened to Warmbier.

Richardson, a Democrat, credited the State Department with securing Warmbier’s return from North Korea without any preconditions but said a forceful response from the U.S. government would be required “if it’s determined that there was a cover-up and Otto’s condition was not disclosed and he didn’t get proper treatment.”

Such detentions in the totalitarian nation have added to tensions between Washington and Pyongyang.

The U.S. government accuses North Korea of using such detainees as political pawns. North Korea accuses Washington and South Korea of sending spies to overthrow its government.

Secretary of State Rex Tillerson said last week that the State Department was continuing “to have discussions” with North Korea about the release of the other imprisoned Americans.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)