North Korea held 22-year-old Otto Warmbier for 17 months.
Pyongyang said the University of Virginia student fell into a coma after contracting botulism and taking a sleeping pill.
But after his release from the communist nation, doctors in Cincinnati who examined him said they found no sign of botulism or sleeping pills in his system, and no evidence of beatings.
What an MRI showed was that Warmbier was missing an extensive amount of brain tissue.
Someone or something inflicted enough damage to leave the young man in a vegetative state.
Neurologist Dr. Daniel Kantor of UC Health told reporters Warmbier's "neurological condition can be best described as a state of unresponsive wakefulness."
"He has spontaneous eye opening and blinking; however, he shows no signs of understanding language, responding to verbal commands or awareness of his surroundings," Kantor explained.
Experts have been left guessing how or why this happened.
North Korea sentenced Warmbier to 15 years of hard labor for allegedly trying to steal a propaganda banner.
For some perspective on life in communist North Korea, CBN News interviewed Jared Brock, co-founder of Hope for the Sold. In 2014, Brock traveled to North Korea as part of a 37-thousand mile journey to several countries around the world. He documented his travels in the book A Year of Living Prayerfully.
At his trial in North Korea, Warmbier pleaded with the court, saying tearfully, "Please save my life. Please think of my family."
After Warmbier's death, President Donald Trump issued a statement blasting "the brutality of the North Korean regime."
The question now is how the U.S should respond to a rogue state that holds 3 other Americans hostage, and continues to perfect both nuclear weapons and long range missiles.
Warmbier's father, Fred Warmbier, said he is "just tremendously proud of Otto." He said his son was a "thrill seeker" who wanted to see North Korea.
With his death, the family said Otto Warmbier "has completed his journey home."