American hostage Kayla Mueller shared her strong faith in Jesus Christ in a letter before she was killed after she was captured by the ISIS terrorist group.

Mueller's grieving parents Carl and Marsha Mueller recently shared their daughter's inspirational letter after it was confirmed that their beloved daughter is no longer alive.

"I remember Mom [Carol] always telling me that all in all in the end the only one you really have is God. I have come to a place in experience where, in every sense of the word, I have surrendered myself to our creator b/c literally there was no else.... + by God + by your prayers I have felt tenderly cradled in freefall," wrote Mueller in the letter while being held captive by ISIS.

Mueller also revealed how God set her free even though she was physically being held against her will by the extremist group.

"I have been shown in darkness, light + have learned that even in prison, one can be free," wrote Mueller.

"I am grateful. I have come to see that there is good in every situation, sometimes we just have to look for it. I pray each day that if nothing else, you have felt a certain closeness + surrender to God as well + have formed a bond of love + support amongst one another."

The young humanitarian from Prescott, Arizona was kidnapped by ISIS when she was helping refugees in Syria in August 2013.

"I miss you all as if it has been a decade of forced separation. I have had many a long hour to think, to think of all the things I will do w/ Lex, our first family camping trip, the first meeting @ the airport. I have had many hours to think how only in your absence have I finally @ 25 years old come to realize your place in my life," wrote Mueller to her family in the emotional letter.

"Please be patient, give your pain to God. I know you would want me to remain strong. That is exactly what I am doing. Do not fear for me, continue to pray as will I + by God's will we will be together soon.

"All my everything, Kayla."