By Paul LeBlanc

CNN

(CNN) -- After 17 months of detention in North Korea, the conditions of which are still unclear, Otto Warmbier returned to his home state of Ohio Tuesday night.

But the young man who landed in Cincinnati and was immediately taken to a hospital isn't the same person who left a year and a half ago on a trip to explore the secretive country.

Since his return, Warmbier hasn't talked, moved in any purposeful way or responded to verbal communication. In a news conference Thursday, doctors called his condition "unresponsive wakefulness," and revealed he had suffered significant brain damage during his imprisonment.

The North Korean government said botulism is to blame for Warmbier's condition, but doctors haven't found any evidence of the illness in the now 22-year-old.

Before his detention made global headlines, Otto Warmbier was just an adventurous college student.

Bright future

Otto was born to Cindy and Fred Warmbier in Cincinnati -- the same city in which he's now hospitalized.

He excelled in academics, graduating from Wyoming High School in 2013 as his class salutatorian and getting a scholarship to the University of Virginia. There, he studied commerce and economics and was a member of the Theta Chi fraternity.

By all accounts, Warmbier was a planner. Someone who would always prioritize family and schoolwork over socializing.

"If Otto had anything schoolwork-related, job-related, family-related that he needed to do," Otto's friend Ned Ende told the Washington Post, "there was absolutely nothing you could say to him to convince him to do stuff with you."

But instead of graduating in May with the rest of his class, Warmbier was still in North Korea.

It wasn't a part of the plan.

Eye for adventure

In the spring of 2016, Warmbier signed up for a trip to North Korea with the Young Pioneer Tours travel group, a company that takes participants to places they wouldn't normally go.

"Otto was just a really great lad," Danny Gratton, Otto's roomate on the trip, told the Washington Post.

"I got to know Otto really, really well. He was such a mature lad for his age."

In pictures and videos from his time in North Korea, Warmbier can be seen smiling and enjoying himself.

One image taken during the trip shows Warmbier throwing a snowball and laughing.

"This is the Otto I know and love," Warmbier's brother Austin told CNN affiliate WCPO. "This is my brother."

In total, the trip was supposed to last five days. Warmbier had plans to visit Beijing, China, after he left North Korea.

But as he tried to depart from Pyongyang's airport, he was stopped in security.

According to the North Korean government, Warmbier was detained because he had sneaked onto a restricted floor of his hotel and had stolen a political poster.

The next time the world saw Warmbier he was distraught, breaking down in front of Korean journalists in a video released by North Korea in February of 2016. He admitted to the crime and begged for forgiveness and for his release. It's not known whether his confession was voluntary.

For his alleged crime, Warmbier was sentenced to 15 years of hard labor. In the end, he spent 17 months in North Korea before being released. He was taken by a medical aircraft to the US.

Uncertainty ahead

It's not clear what lies ahead for Warmbier. Doctors at the University of Cincinnati Medical Center say his condition, while stable, is severe, and that he suffered extensive loss of tissue in all regions of his brain.

The circumstances under which he came to be in that state remain a mystery.

In a news conference on Thursday, Warmbier's father called his return bittersweet.

"[I feel] relief that Otto is now home in the arms of those who love him," he said. "And anger that he was so brutally treated for so long."