Actually, this is the perfect time to show that this is exactly the moment when Second Amendment lawful carry of equally deadly weapons should be demonstrated everywhere lest there be a copycat shooter ready to start his/her own mayhem.
Where were the concealed carry patrons at the El Paso incident? This young man might have simply been asked by a store manager or roaming security to consider the effect on other patrons, or even walk around with the young man to see that his freedom to carry open in the store was not interfered with. I believe that all Walmarts have (armed ?) security in clerk's disguise walking around the store to recognize and deal with difficult situations.
I believe the Walmart was in a mall that was gun-free
Or it could have been a good time for some trigger-happy patron to shoot him dead before he opened fire.