Story highlights Otto Warmbier died Monday after being in a persistent vegetative state, his parents report

College student suffered severe brain damage during 17 months of detention, doctors said

(CNN) Otto Warmbier, the former North Korean detainee now back in the United States, died Monday, his parents reported in a statement.

The 22-year-old college student suffered severe brain damage during his 17 months of detention, doctors at the University of Cincinnati Medical Center said in reporting his condition Thursday. At that time, Warmbier continued to suffer from "unresponsive wakefulness," also known as a persistent vegetative state, meaning he was awake at times but not aware of his surroundings or himself.

"When Otto returned to Cincinnati late on June 13th he was unable to speak, unable to see and unable to react to verbal commands," his parents explained Monday, describing his appearance as "very uncomfortable -- almost anguished."

The family thanked the efforts of the "wonderful professionals at the University of Cincinnati Medical Center."

"Although we would never hear his voice again, within a day the countenance of his face changed -- he was at peace. He was home and we believe he could sense that," they said.

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