The operation to kill the world's most wanted terrorist, the Islamic State group's Abu Bakr al-Baghdadi, was named after American aid worker and former ISIS hostage Kayla Mueller.

And on finding out that the operation had been named for her daughter, Marsha Mueller started to cry.

"Gosh what a gift, for Kayla and for us," she told NBC News. "It also lets us know that this administration did not forget about Kayla and was trying to help us find Kayla."

Families of ISIS' victims and survivors of the hyperviolent jihadis lauded President Donald Trump and U.S. troops after the group's brutal leader was killed in a U.S.-led raid in northwestern Syria on Saturday.

Kayla Mueller, an American humanitarian worker from Prescott, Arizona, with her mother Marsha Mueller. Reuters file

Mueller was captured in Syria in August 2013 after heading to the Turkish-Syrian border in December 2012 to work with refugees. She was killed in 2015.

Mueller’s parents said that they spoke directly with Trump after the operation, and pressed for more information about their daughter, including details on where she is buried.

“Justice was brought to those Americans who were so brutally killed, as were others, as the president pointed out,” national security adviser Robert O'Brien said on NBC’s Meet the Press on Sunday.

Al-Baghdadi, who had led ISIS since 2010, had a a $25 million U.S. bounty on his head. He declared himself caliph, sovereign over all Muslims, in 2014, and was reviled for violence against religious minorities, the imposition of a fanatical version of Islam in the territories the group controlled, and terror attacks around the world.

The mother of former ISIS hostage James Foley, who was killed in 2014, also praised the operation and pressed for U.S. intervention to help other Americans held in the region, including journalist Austin Tice, who went missing in Syria in 2012, and psychotherapist Majd Kamalmaz, who has been missing in Syria since 2017.

“I would love to see the same American expertise used to free innocent American hostages who are held around the world, and we know of about a dozen in Syria,” Diane Foley said in an interview with NBC News.

Journalist James Foley in 2011. Steven Senne / AP file

"Jim did not like violence, and I think he would want our country to show how justice is best served through our court of law. I think that's what he'd most want to see," she added.

In 2013, journalist Steven Sotloff vanished in Syria. A year later, ISIS released a video of his beheading.

His parents, Art and Shirley Sotloff, put out a statement thanking those involved in the al-Baghdadi operation and pushed for the continued involvement of the U.S. to fight ISIS.

"It is our hope that our son's surviving captors, nicknamed 'the Beatles,' will be brought to justice, that all remaining hostages are returned to safety, and that the United States will take every measure to eliminate the resurgence of ISIS and terror in all forms," the statement read.

The family of American aid worker Abdul-Rahman Kassig, who was captured in 2013 and killed by ISIS in 2014, made a plea for peace following the raid.

“We pray, especially today, that all those who are affected by warfare and hate may find light," a statement released by the family read.

One of the groups most affected by ISIS were the Yazidis, adherents of one of the Middle East’s oldest religions, whom ISIS targeted for extermination. Thousands of Yazidis were slaughtered on their ancestral mountains in northwestern Iraq, and Yazidi women were taken as sex slaves for ISIS militants.

"ISIS caused a deep wound inside us. It is not going to be healed at all," said Sadeq Khudeda, 48, who fled his home in Sinjar in the middle of the night when ISIS took control.

"I lost two of my cousins. They were killed by those terrorists. They raped our women, they tortured then killed our men. They kidnapped our young girls and boys and made them slaves. I am really happy that their leader, the big criminal, was finally killed."

Children believed to be from the Yazidi community are evacuated from the ISIS' embattled holdout of Baghouz in Syria on March 6. Bulent Kilic / AFP - Getty Images

However, he warned that al-Baghdadi’s death was not the end of ISIS in Iraq and pushed for U.S. involvement to defeat the remaining militants.

In Syria, Muawiya Jassim, 37, who lived under ISIS control in Deir ez-Zor, said that al-Baghdadi's death was "the best news I heard in a long time."

Jassim, who now lives with his wife and four children in Hasakah, recalled how they "lived in constant anxiety and fear" under ISIS and how fighters forced them to watch the beheading of a man they said was a thief in front of a mosque.

"They are not Muslims, they are terrorists," he said. "I’m very happy that he finally got what he deserved. I hope that the caliph will burn in hell."

Residents in the former ISIS stronghold of Raqqa said they while they were happy about al-Baghdadi's death, they worried that the group could still make a comeback.

"I was very happy when I heard that al-Baghdadi finally got killed but I don't think ISIS is defeated with al-Baghdadi's death," said Hassoun Abo Darwish, a truck driver who lives in the Syrian city with his wife and three children.

He added that he worried the withdrawal of American troops would result in the return of the group.

“The ideology is still among his believers who are now living undercover between us. ISIS raised a whole generation. There is still much more to do," he said.