Two men who were reportedly killed in combat while fighting the Islamic State group in Syria left suburban Denver neighborhoods for a war zone because of comradery and an unshakeable drive to right an injustice, their families said Wednesday.

Jordan MacTaggart, 22, is believed to have been killed Aug. 3 while fighting in a squad that included two Americans and a Swede, and Levi Shirley, 24, was reportedly killed by a land mine July 14.

It's unclear if the two men crossed paths in Colorado or the Middle East, but their parents on Wednesday highlighted similar motivations for why they joined Kurdish forces against ISIS.

"He had a huge heart and he was always affected by any injustice," Jordan MacTaggart's mother, Melissa MacTaggart, said from the family home in Castle Rock south of Denver. "It would hurt him, probably more than other people, like he couldn't let it go."

Robert MacTaggart said those fighting with his son told him by phone that he was shot in the chest while helping a soldier wounded by an improvised explosive device. The father followed the battles of the Kurdish forces on the Internet and had contact with fighters in Syria to track his son's well-being.

U.S. State Department officials said they are trying to confirm the death.

Like Shirley, Jordan MacTaggart's family said he went to join the fight after hearing about beheadings, stabbings and sexual assaults reportedly committed by ISIS forces. Also like Shirley, he fought in Syria, returned home and then headed back to the battlefield.

Shirley's mother, Susan Shirley, said she thinks her son and others return to fight because they have a hard time readjusting to life in America and "because they get homesick for each other."

"That's a bond you don't share with anyone else," she said Wednesday. "That's an unbreakable bond."

Dozens of other Westerners are now fighting with the Kurds, spurred on by social media campaigners and a sense of comradery and duty rooted in the U.S.-led military intervention in Iraq.

"You've got to figure the idealism of a 20-something guy," Shirley said. "There's that drive. You've got this really strong drive to save the world, and what better way to save the world than to destroy ISIS?"

The first American believed to have been killed fighting ISIS had no military training and died alongside Kurdish forces in 2015. Keith Broomfield of Massachusetts had joined the People's Protection Units known as the YPG, the main Kurdish guerrilla group battling ISIS in Syria.