What possesses ordinary young men to give up everything they have, including bright futures to go overseas and fight for one of the most notorious terrorist organizations... especially if they're Americans?

In a list of ISIS fighters obtained by an NBC News reporter from a defector from the terrorist group, two former students from Texas were listed as combatants. They are:

--Omar Kattan, an alumnus of the University of North Texas in Denton.

--Talmeezur Rahman, an alumnus of Collin College in McKinney.

Kattan, who apparently defected in 2013, is believed to have been killed in Syria according to the NBC report which first aired late Sunday.

The NBC affiliate in Dallas-Fort Worth went the extra mile to find Kattan's and Rahman's friends, neighbors and family members in the North texas area. The general reaction is one of disbelief as seen in the reports.

An updated 12-minute report was released by NBC News Monday with profiles of fifteen American recruits to ISIS.

The latest NBC News video report:

 

Correspondent Engel spoke to MSNBC about the report:

 

Here's coverage from KXAS-TV, NBC 5 in Dallas-Fort Worth: