An NBC News investigation into three Columbus, Ohio, residents who traveled to Syria and joined ISIS was greeted with shock and sadness in some corners of the city nicknamed the "biggest small town in America."
But Columbus Mayor Andrew Ginther said it just showed that terrorism can lurk anywhere.
"While concerning, the fact that individuals linked to ISIS have some connection to Columbus should not be surprising, as no community in America is immune," Ginther said in a statement.
As NBC News reported for "On Assignment" on Sunday night, a three-person cell of ISIS fighters had ties to Columbus.
Siblings Zakia Nasrin and Rasel Raihan grew up in Columbus and a neighboring suburb. After Nasrin married Northern California resident Jaffrey Khan in 2010, they settled in Columbus, and she graduated from Ohio State.
In July 2014, the trio left the United States, and a trove of ISIS personnel files obtained by NBC News shows that Raihan and Khan joined the terrorist organization in Syria.
Related: 15 Who Left the United States to Join ISIS
According to relatives and a senior intelligence source, Raihan, who was just 18 when he signed up to fight, was killed in Syria. Khan and Nasrin, both 24, are working in a hospital in Syria and are parents of a baby girl, family members said.
The elite high school where Nasrin and Raihan earned top grades emailed parents to alert them to the disturbing news about two alumni.
"I was deeply saddened by this news. While Zakia and Rasel graduated some time ago, they are still very much in our thoughts," Meka Pace, executive director of Metro Schools, said in a statement.
"Our condolences and prayers go out to the families of these young adults. Even though their actions are indefensible, the loss of a young life is tragic — no matter the circumstances."
Dominion Middle School, where Raihan was a student from 2008 to 2010, said he was a "great student."
"He was a typical adolescent boy who had high expectations and came from a very humble family," said Jacqueline Bryant, a spokeswoman for the school district.
Mounir Lynch, 19, attended Dominion with Raihan and said he is stunned by the turn his former schoolmate's life took.
"He never had bad behavior," Lynch said. "He was always a positive guy and he was just so brilliant."
"It's just a mystery in general with any American — regardless of your race or religion or background — why they would join this group that is attempting to tear the world apart," he added.
Lynch said it angered him that his old friend would put American security at risk and in doing so, make life harder for law-abiding Muslims.
"We don't know how he got killed or anything like that," he said. "We just know that his choice ended up costing him his life and his dignity."
