President Donald Trump on Thursday defended leader Kim Jong Un over the death of Otto Warmbier, an American college student who died after being imprisoned in North Korea. The president's remarks at a news conference in Vietnam came as a surprise, considering Trump previously said Warmbier was "tortured beyond belief" during his imprisonment. Conservatives, including former Sen. Rick Santorum, decried his comments as "reprehensible."

» RELATED: Trump: I don't think North Korea's Kim had role in US student's death

Here’s what you should know about Otto Warmbier

Where was he from?

Warmbier was born in Cincinnati, Ohio, on Dec. 12, 1994, to Fred and Cindy Warmbier. He graduated from Wyoming High School in 2013 as class salutatorian and earned a scholarship to the University of Virginia, where he was studying economics.

When and why was he in North Korea?

Warmbier, a member of the university's Theta Chi fraternity, already had plans to study abroad in Hong Kong during college. Seeking some adventure before long days of work ahead, he decided to join a travel group popular for budget excursions to "destinations your mother would rather you stay away from" — like North Korea. "The State Department had an advisory in place against traveling to North Korea, where he'd be beyond the American government's power to directly help him," according to a GQ profile published last July.

He met fellow Young Pioneers travel group members in China before flying to Pyongyang.

What happened before Warmbier’s arrest?

With the travel group, Warmbier explored sights curated especially for foreign tourists (a seized U.S. spy ship, statues of North Korean dictators, a 47-story tower of Western luxuries). He and his new friends even threw snowballs with local North Korean children.

But according to GQ, on the night the group celebrated New Year's Eve out in the main square, there's a two-hour span in which friends don't recall seeing Warmbier at all.

When his roommate returned to their room around 4:30 a.m. New Year’s Day, the Ohioan was already asleep.

On their way out of North Korea on Jan. 2, 2016, Warmbier was stopped by authorities at the Pyongyang International Airport.

What led to his imprisonment?

During those mystery hours on Jan. 1, Warmbier allegedly tried to steal a propaganda poster from Yanggakdo International Hotel, where he was staying with the group. North Korea released "grainy CCTV camera footage of an unidentifiable figure removing a framed propaganda poster from a wall in a restricted area of the hotel, claiming it was Otto," according to GQ.

The poster stated, "Let's arm ourselves strongly with Kim Jong-il's patriotism!" The act of misusing, harming or stealing such items is considered a serious crime in North Korea. Warmbier was arrested and sentenced to 15 years in prison with hard labor.

He ultimately admitted to the crime and begged for forgiveness. "I have made the single worst decision of my life. But I am only human.… I beg that you find it in your hearts to give me forgiveness and allow me to return home to my family," Warmbier said in a tearful confession six weeks later. The video was released in February 2016. According to CNN, we still don't know whether the confession, in which Warmbier stated he plotted to steal the poster "at the prompting of a local Methodist church, a university secret society, and the American administration," was voluntary. Warmbier was Jewish and not affiliated with a Methodist church.

» RELATED: Trump accepts Kim 'word' he had no role in Warmbier death

What happened during his imprisonment?

It's still unclear what exactly happened during his 17 months of detention in North Korea, but doctors said he had suffered significant brain damage. North Korean government officials, however, said Warmbier suffered botulism, a rare but serious illness caused by a toxin that can weaken the body's muscles and can ultimately lead to death, according to the Atlanta-based Centers for Disease Control and Prevention.

According to North Korean officials, Warmbier had fallen into a coma after taking a sleeping pill after contracting food-borne botulism.

American doctors found no evidence of botulism.

What led to his release?

In June 2017, Trump learned that Warmbier was unconscious and had an American team fly to North Korea. At approximately 8:35 a.m. on June 13, 2017, then-Secretary of State Rex Tillerson called the president to let him now Warmbier was on the way home, according to CNN. But his parents were warned that “Otto had been unconscious for months, according to the North Koreans.” Ohio Sen. Rob Portman told Warmbier’s mother her son appeared to have severe brain damage.

Still, “the Warmbiers were optimistic, up-by-their-bootstraps patriots, and they hoped that with American health care and their love, their son might again become the vivacious person he'd been when he left,” they told GQ.

» RELATED: Doctors say Otto Warmbier has 'extensive loss of brain tissue' on return from N. Korea

What happened when he returned to America?

Upon news of his release, parents Fred and Cindy “waited in agony” for the son they hadn’t spoken to for a year a half. When Warmbier arrived in Ohio on a private plane on the evening of June 13, 2017, crowds donning handmade signs welcomed him home. But the young man who landed in Cincinnatti wasn’t the same person anymore.

Doctors at the University of Cincinnatti Medical Center said Warmbier had suffered "extensive loss of tissue in all regions of his brain," CNN reported. "The circumstances under which he came to be in that state remain a mystery."

There was no evidence of botulism and no evidence of physical abuse of torture, yet his brain was deprived of oxygen and ultimately led to a cardiac arrest.

When did Warmbier die?

He died on June 19, 2017, in Cincinnatti. Warmbier was 22 years old. After being in a persistent vegetative state for days, his feeding tube was removed. Though he had been able to breathe on his own, he could not make purposeful movements and was unaware of his environment and language. Doctors believe his cardiac arrest may have been triggered by a respiratory arrest.

“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,” his family said in a statement.

A North Korean spokesman later said, “Although we had no reason at all to show mercy to such a criminal of the enemy state, we provided him with medical treatments and care with all sincerity on humanitarian basis until his return to the U.S., considering that his health got worse.”