I agree. This is going to get dicey.
Here's the statute on making a terrorist threat in Missouri.
2016 Missouri Revised Statutes :: TITLE XXXVIII CRIMES AND PUNISHMENT; PEACE OFFICERS AND PUBLIC DEFENDERS (556-600) :: Chapter 574 Offenses Against Public Order :: Section 574.120 Making a terrorist threat, second degree--penalty.
From the video I posted, this guy was carrying that rifle properly. You're supposed to either carry it the way he is, or have it strapped over your back. It wasn't up against his shoulder like he was getting ready to fire.
That takes care of subsection one. Where is the "implied threat?"
Subsection 2 does not apply.
Subsection 3 does not apply.
If the guy was not breaking any law, then one may argue that the manager should be charged with making a terrorist threat by pulling the fire alarm and causing panic.
Remember, you can't yell fire in a movie theater if there's no fire.
Subsection 3 applies.
(3) Causes a false belief or fear that an incident has occurred or that a condition exists involving danger to life.)
Here's the exception. It is also marked subsection 3.
(3. No offense is committed under this section by a person acting in good faith with the purpose to prevent harm.)
One could argue that the reason he was armed is because after El Paso, he was acting in good faith with the purpose to prevent harm to himself and the public from a real shooter entering Walmart and opening fire.
If he didn't break any law, is it his fault that the public may not be aware of the law, and what he was doing was perfectly legal?
If what the fireman did was acceptable, would it have been just as acceptable if he saw the fireman carrying a gun and held him at gunpoint?
One thing I think is safe to say. By next week, you'll be seeing signs at the door of Walmart saying "no guns allowed." IMO.