A vigil was held at the University of Arizona on Monday (9 February) for American hostage Kayla Mueller, who Islamic State (Isis) says was killed in a Jordanian air strike hours before confirmation of her death came Tuesday morning.
More than 30 people gathered at Arizona State University in Tempe, Arizona to take part in the vigil sponsored by the Muslim Liberty Project.
Mueller was the last-known American hostage held by IS, which controls wide areas of Syria and Iraq. The militant Islamist group has beheaded three other Americans, two Britons and two Japanese hostages - most of them aid workers or journalists - in recent months.
Mueller, from the small city of Prescott about 100 miles north of Phoenix, felt compelled to help others from an early age, according to a statement from the family.
US President Barack Obama said in a statement the US will "find and bring to justice the terrorists who are responsible for Kayla's captivity and death".
Mueller relocated to the Turkish-Syrian border in December 2012 to help Syrian refugees, working with the Danish Refugee Council and the aid group Support to Life. She was taken by IS while leaving a hospital in the northern Syrian city of Aleppo in August 2013.