Credit also to the gunman for being as cool as a cucumber.
The lack of “extraneous” action on his part leads me to suspect that he was possibly an LEO or military combat veteran. Someone who understands what guns are and do, and is quite practiced with them.
My first thought would be veteran, but because once the suspects were arrested, he was given quick clearance to take off suggests an LEO who does not want his face on the front page.
In any case, he “done good”.
Or he might just be a regular Texan.
Some of us have been training since birth.