You can open carry in Texas if you have a permit to do so. Getting licensed is kind of a joke but you can walk around with a rifle on your back or a gun on your hip.
What you CAN'T do is wave the gun in the air yelling God is Great or Trump 2020. Thats called "brandishing" and is considered a threat.
Arguing with someone in the parking lot of Whataburger? Don't pull up your shirt and show the gun tucked into your belt. Brandishing.
Someone walking up your driveway to put a flyer for a new pizza place on your door and you walk out holding a shotgun? Brandishing.
My point is, how did they know that the drivers were armed? Were they presenting the guns? Were they waving them out of the window, yelling "God is Great"?
Also, it looks like its happening here today.