An American school teacher who was captured on the battlefield in Syria by US-backed Kurdish forces gave an interview with NBC News, which airs on Tuesday.

In the interview, 34-year-old Warren Christopher Clark said he joined the terrorist group ISIS because he wanted to "see exactly what their group was about."

A resume and cover letter found in a home in Mosul, Iraq, have been attributed to Clark, who confirmed in the interview he sent them in 2015 because he needed to find a way to support himself.

He said he wasn't daunted by videos he had seen of ISIS fighters conducting executions and crucifixions, saying he saw no difference between them and executions in Texas.

Warren Christopher Clark told NBC News that he has no regrets about his decision to join the Islamic State. The interview, which takes place at an undisclosed location in Syria, airs on Tuesday.

The 34-year-old former substitute teacher from Texas said he sought out the terrorist group in June 2015.

The resume and cover letter were discovered in a home in Mosul, Iraq, and eventually obtained by George Washington University's Program on Extremism. Clark told NBC he sent the resume from Iraq, where he was living at the time, because he needed a way to support himself.

Read more: US-backed forces in Syria just captured a substitute teacher from Texas who had sent his resume to ISIS

"I wanted to learn more about the ideology. I'm a political science major, global business minor. I like politics. I like travel, world events. That's what I wanted to do," he said in the interview.

He claims he did not personally take up arms or fight for the Islamic State, but he became very familiar with the sound of airstrikes.

"It was a place that was constantly being bombed," he said in the interview. "You were always on edge. Day and night, just bombs and airstrikes."

Clark said over the course of three years in the caliphate, he witnessed "executions and crucifixions." He compared the executions conducted by ISIS fighters to those in his home state of Texas.

"I'm from the United States, from Texas," he said in the interview. "They like to execute people, too. So I really don't see any difference. They might do it off camera, but it's the same."

According to NBC, the Texan converted to Islam, but it is not clear when. He was captured by US-backed Kurdish forces and is being held in their custody in Northern Syria. According to The Guardian, the Islamic State has lost around 95% of the territory it once held.