The government of North Korea sentenced Otto Warmbier, an American student at the University of Virginia, to 15 years of hard labor for “subversion” on Wednesday.

So how did the 21-year-old economics major subvert North Korea? Specifically, Warmbier was convicted of removing a political banner from the wall of a Pyongyang hotel, pondering stealing it, and then leaving it on the floor.

Warmbier confessed to the crime last month in a dramatic, emotional press conference that North Korean officials say he requested himself. Reading from a statement, the American student wept and bowed at the waist, hanging his head in shame.

“I entirely beg you, the people and government of the DPRK, for your forgiveness,” he said at the conference. “Please! I have made the worst mistake of my life!"

It is not clear how much of the confession was coerced.