He was a 42 year old from Texas who was active duty in the Army for 9 years and deployed to Afghanistan. All the reports of him coming over from Mexico were premature by people who wanted that narrative to be true.
I'm still seeing many reports that he converted to Islam and has actually been reported to the COC by other individuals over his radicalized behavior. Now, that's not definitely true.. but it sure seems to be point to a radicalized Muslim, regardless if he was born that way or not.