Both the U.S. government and Kayla Mueller's family have confirmed the American aid worker held captive by ISIS is dead.

The news comes days after ISIS claimed Jordanian bombings had killed the hostage, though the U.S. and coalition forces were skeptical. No information on how Kayla died has been released.

According to The New York Times, the family released a statement on Tuesday after finding out Kayla, 26, had passed away. They did not specify how they found out she died.

"We are heartbroken to share that we've received confirmation that Kayla Jean Mueller, has lost her life," Carl and Marsha Mueller, Kayla's parents from Prescott, Arizzona, said in the statement. "We are so proud of the person Kayla was and the work that she did while she was here with us. She lived with purpose."

A family representative, speaking on condition of anonymity, said the family received a message over the weekend from her captors with "additional information which the intelligence community authenticated and deemed credible."

The family also released a letter smuggled out of Syria in which Mueller explains she was being treated well. The letter seemed to confirm she had not endured the brutal treatment male captives underwent.

In a statement, Secretary of State John Kerry remembered Mueller's good work and condemned ISIS for her death.

"All Americans mourn the loss of Kayla Mueller, a compassionate young American who represented everything good about the human spirit. There are no words to express to Kayla's parents, Marsha and Carl, how sorry we are for their crushing loss, just how much so many wished for and worked to try and secure a better outcome, or how awe-inspiring is the example of their strength, determination, and devotion to faith and family," he said, adding that the country mourns with them.

He recounted Mueller's humanitarian work both in the U.S., working at an HIV/AIDS clinic, to her work in Palestine and Turkey.

"Kayla's sense of values, her humanity and generosity, her idealism -- this is what will endure, and it will endure long, long after the barbarity of ISIL is defeated," he said and added that the U.S. and its allies will continue to fight against ISIS.

The White House also released a statement mourning Mueller, recounting her values and work.

"Kayla represents what is best about America," the statement said.

The White House then attacked ISIS but did not reveal the circumstances surrounding her death.

"ISIL is a hateful and abhorrent terrorist group whose actions stand in stark contrast to the spirit of people like Kayla. On this day, we take comfort in the fact that the future belongs not to those who destroy, but rather to the irrepressible force of human goodness that Kayla Mueller shall forever represent."

ISIS previously claimed Mueller died in the series of Jordanian bombings over Raqqa, the group's de-facto capital, over the weekend. However, both Jordan and the U.S. remained skeptical.

Kayla was believed to be the last American hostage the Islamist extremist group ISIS held, after she was kidnapped in Syria in 2013.

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