North Korea has denied mistreating Otto Warmbier after the American student was returned to the US in a coma.
The 22-year-old died on Monday having being brought back to Ohio last week.
His family blame the pariah state and parents Fred and Cindy Warmbier said in a statement: 'The awful torturous mistreatment our son received at the hands of North Koreans ensured that no other outcome was possible beyond the sad one we experienced.'
But the North Korean government say the death is a 'mystery' and denies responsibility.
They blame his coma on botulism – a form of bacterial poisoning – a possibilty which the family and US government deny. But in an apparently contradictory statement, after telling his family that Warmbier had been in a coma since his trial more than a year ago, a Pyongyang spokesman later said he was returned to America in a 'normal state of health'.
He said: 'The fact that Warmbier died suddenly in less than a week just after his return to the US in his normal state of health indicators is a mystery to us as well.'
Warmbier was initially arrested at Pyongyang airport in January 2016 and accused of stealing a propaganda sign from a hotel.
His family heard no news of him until June 13, 2017 when North Korean officials announced he had been in a coma since his trial.
More than 2,500 family, friends and supporters gathered for Warmbier's funeral on Thursday.
Kenneth Bae, a Christian missionary who was held in North Korea himself, said: 'I cannot understand what the Warmbier family is feeling right now. But I mourn with them, and I pray for them. No words can ease this pain, but we can pray for them. It's my hope and prayer that they also know others in America are mourning with them and will not forget their son and brother.'
The family's statement thanked people for their support and prayers.
'We thank everyone around the world who has kept him and our family in their thoughts and prayers. We are at peace and at home too,' they said.