Two college students from North Texas left the United States to fight for ISIS, according to personnel records from the terrorist group obtained by NBC News.

Omar Kattan, a former biology student at the University of North Texas in Denton, entered Syria in September 2013 when he was 23 and described himself as a "suicide fighter," according to the records. He is believed to have been killed.

Talmeezur Rahman, a computer major at Collin College in McKinney, disappeared from the U.S. in 2014, and his "fighting name" was listed on ISIS documents, NBC News reported.

The two names were on a thumb drive that an apparent ISIS defector gave to NBC News correspondent Richard Engel in Turkey.

The files were verified by counter-terrorism specialists, NBC News said.

The network reported the names on Sunday.

Omar Kattan

Kattan, whose family apparently still lives in Denton, attended UNT from 2007 to 2011 and graduated with a degree in biology, said UNT spokeswoman Margarita Venegas.

She declined further comment.

He also worked briefly at Texas Woman's University in Denton as a lifeguard and a group exercise instructor from May 17 to Aug. 31, 2012, the university said.

In an online post, he wrote, "I'm a biology major at the University of North Texas. I'm a senior with a minor in physics, chemistry and Arabic, currently I'm a teacher's assistant in the Arabic Department and I like my job a lot."

He said he planned to go to dentistry school.

"I hope my country Syria will be free," he added.

Kattan is believed to have been killed, NBC News reported, citing a former law enforcement official.

Talmeezur Rahman

Rahman, 22, was born in India and grew up in Kuwait, before coming to live with distant cousins in Frisco. His relatives in North Texas said they are "extremely shocked" to learn Rahman joined ISIS.

He studied computers at Collin College from January 2012 to May 2014 and made the President's List for good grades his first year, but never completed the Associate of Science degree he pursued before joining ISIS.

Rahman first attended classes at the Preston Ridge campus in Frisco, then left his relatives' home for the Spring Creek campus in Plano, where he lived in student housing.

"Very scary to think that. It's pretty safe here, so to know that someone joined ISIS from here is pretty intimidating," said Collin College student Taryn Swanepoel.

His relatives in Frisco say Rahman grew distant after moving to Plano, and then he left the country abruptly two years ago.

NBC News quoted his father as saying he reported his son missing in 2015.

"I am searching for him for almost two years," his father said. "I am really frustrated."

The Islamic State's files listed Rahman's "fighting name" as Abu Salman al-Hindi and said that although he was highly educated in computers, he didn't work because he "has a beard in America," NBC News reported.

His father said he was surprised to learn his son may have joined ISIS because he was very serious about his school work.

"I don’t believe he can have a mind to do anything else," he said.

Rahman's current whereabouts are unclear.

NBC 5's Kevin Cokely contributed to this report.