Otto Warmbier, the US student freed from North Korea, has died. His family made the announcement in a statement released by his Ohio hospital.

Warmbier came back to Cincinnati last week in a coma after 18 months held in custody in North Korea.

Warmbier’s family learned that the University of Virginia student has been in a coma since March 2016, and the UC Health doctors said Thursday that he apparently suffered “respiratory distress,” and the oxygen supply to the brain was cut off.