PRESCOTT, Ariz. -- Friends say the American woman taken hostage by Islamic State militants was determined to get to Syria and learned Arabic so she could perform aid work and advocate for causes in the Middle East.

Kayla Mueller, 26, travelled to the Palestinian territories, Israel and other countries before deciding a couple years ago that it was her calling to help the people of Syria, friends said Wednesday. She moved to an area in Turkey near the Syrian border, and about eight months later, she was captured in Syria by Islamic State militants. Her death was confirmed this week by her family and U.S. government.

Friends say Mueller often talked about going to Syria after she graduated Northern Arizona University, and they said she was determined to get there, despite the risks.

"She had determined over many years of serious internal questioning that the best way to deal with the suffering in the world was to face it directly, and to address it on the ground," said Leslie Alamer, who attended university with Mueller.

Mueller's trip from Turkey across the border into Syria in August 2013 was a dangerous move given the bloodshed that has gripped the country under the regime of embattled President Bashar Assad. Nearly half of Syria's population has been displaced, and some 200,000 people have died in the fighting and crossfire.

What exactly happened to Mueller in the year and a half she spent in captivity and how she died remained unclear Wednesday. The U.S. Embassy in Syria is closed, and the CIA has no permanent presence on the ground. Family members have not said if they know how Mueller was treated in captivity, including if she was tortured. Three other Americans were beheaded by Islamic State militants last year.

President Barack Obama said a military operation last summer to recover Mueller and others failed when rescuers arrived only "a day or two" after the group had been moved.

Sen. John McCain and Rep. Paul Gosar of Arizona worked various channels to help rescue her, to no avail. Gosar said the Islamic State group was interested in a swap involving Aafia Siddiqui, a Pakistani scientist convicted of shooting at two U.S. soldiers in Afghanistan. Gosar said his chief of staff went to a refugee camp in pursuit of information but wasn't able to find anything out.

McCain said that when he would visit the Middle East, he pressed leaders, including the emir of Qatar, to do what they could to help locate Mueller.

"I got commitments they would do everything they could and were doing everything they could and they did have some leads from time to time," McCain said. "Frankly, I never got anything really hard out of them."

He said he knew few concrete details about what rescue efforts were undertaken on her behalf. He said he learned of a ransom attempt, but didn't know exactly how much her captors were demanding.

Mueller's former roommate at Northern Arizona University, Emily Schick, said Wednesday that she had no doubt that Mueller was doing what she was called to in life.

"Kayla did not see herself as above or separate from the suffering around her," she said.

In Mueller's hometown of Prescott, Arizona, her family encouraged people to donate to organizations Mueller would have supported, saying big displays of support wouldn't mesh with her humble nature.

In 2010, Mueller spent time with the International Solidarity Movement, a group of foreign activists who come to the West Bank and east Jerusalem to show support for the Palestinians. Organizer Abdullah Abu Rahmeh said a protest Friday would be dedicated to Mueller.

Mueller wrote passionately about conditions in Syria. "Every human should act. They should stop this violence," she wrote in a blog post.