Sen. John McCain said Monday night that Otto Warmbier, the University of Virginia student detained by North Korea for more than a year, was "murdered by the Kim Jong-un regime."

McCain's statement came after Warmbier's family announced the 22-year-old student, who was in a coma upon his return to the U.S., had died shortly after North Korea released him.

"I was saddened to learn about the death of Otto Warbier today following his unjust imprisonment and torture in North Korea," said McCain, R-Ariz., who was a prisoner of war in Vietnam. "I send my heartfelt condolences to Otto's family and friends as they grieve this tragic loss."

"Let us state the facts plainly: Otto Warmbier, an American citizen, was murdered by the Kim Jong-un regime. In the final year of his life, he lived the nightmare in which the North Korean people have been trapped for 70 years: forced labor, mass starvation, systematic cruelty, torture and murder...The United States of America cannot and should not tolerate the murder of its citizens by hostile powers."

Warmbier was detained at Pyongyang Airport in North Korea in January 2016. The following March, North Korean officials sentenced him to 15 years of hard labor for allegedly committing a "hostile act" against the country after security footage emerged of him attempting to steal a banner hanging in his Pyongyang hotel.

He was released last week and returned home to his family in Ohio. Warmbier was in a coma, and doctors at the University of Cincinnati Medical Center said Thursday the UVA student was in a state of "unresponsive wakefulness" and suffered loss of brain tissue.

Sen. Marco Rubio, R-Fla., issued his own statement on Twitter. "Otto Warmbier should never have been in jail for tearing down a stupid banner. And he most certainly should not have been murdered for it."

President Trump also condemed North Korea for its treatment of Warmbier but stopped short of accusing North Korea of murdering the American student. In a statement, Trump denounced "the brutality of the North Korean regime."

Secretary of State Rex Tillerson, in a statement late Monday, said the U.S. holds "North Korea accountable" for Warmbier's "unjust imprisonment."

"On behalf of the entire State Department and the United States government, I extend my condolences to the Warmbier family, and offer my prayers as they enter a time of grief no parent should ever know," Tillerson said.

"We hold North Korea accountable for Otto Warmbier's unjust imprisonment, and demand the release of three other Americans who have been illegally detained."

United Nation's Ambassador Nikki Haley released her own statement slamming North Korea's violent regime.

"Countless innocent men and women have died at the hands of the North Korean criminals, but the singular case of Otoo Warmbier touches the American heart like no other," Haley said.