The official confirmation has been given to the parents of Kayla Mueller, the last American hostage in Islamic State custody, that she is indeed dead.

The White House said that Mueller’s family received a private message from her captors over the weekend and the information contained in that communication was authenticated by the U.S. intelligence community. It was not immediately clear how and when Mueller died.

“We are heartbroken to share that we’ve received confirmation that Kayla Jean Mueller, has lost her life,” Carl and Marsha Mueller said in a statement. “Kayla was a compassionate and devoted humanitarian. She dedicated the whole of her young life to helping those in need of freedom, justice, and peace.”