Complex sentence: Kayla Jean Mueller was a humanitarian aid worker from Prescott, Arizona taken captive in August 2013 in Aleppo, Syria, while leaving a Doctors Without Borders hospital.
Split into simpler sentences: Kayla Jean Mueller was a humanitarian aid worker from Prescott, Arizona. She was taken captive in August 2013 in Aleppo, Syria, while leaving a Doctors Without Borders hospital.