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 camaraderie 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 the Islamic State.

"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."

It's been estimated that "hundreds" of foreigners have joined Kurd forces in their battle against the Islamic State, The Christian Science Monitor reported in June 2015 when Keith Broomfield was the first reported case of an American killed while fighting alongside Kurdish fighters.

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.

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

Like Mr. Shirley, Jordan MacTaggart's family said he went to join the fight after hearing about beheadings, stabbings, and sexual assaults reportedly committed by IS 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 US-led military intervention in Iraq.

Get the Monitor Stories you care about delivered to your inbox. By signing up, you agree to our Privacy Policy

Anna Mulrine reported for the Monitor that even US Army veterans are pulled to the clear purpose of fighting IS.

[M]any foreign fighters who have opted to fight against IS say they are seeking a greater sense of purpose. Some US veterans add that they see in the anti-IS fight a clear vision of the enemy that they never found in combat. Others want to complete combat work they feel was left unfinished or undone by the advance of IS 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.