This Phoenix AZ news item goes in my; "What? Huh? Who?" file.
The school staff & administrators
over-reacted in this incident.
A military service member, sworn LE officer, security guard or any other uniformed professional should be able to go on school property w/o being hassled.
People who are "afraid of guns" or "scared" by armed professionals/armed citizens should learn & understand the law(s) of their state/municipality.
Doing security work, I tend to avoid wearing my full uniform & duty belt(sidearm) off duty or while in transit to/from the job location because it can sometimes draw undue attention or cause confusion in some places.
It could also mark you as a automatic target in a armed robbery or violent crime.
I also like to change clothes prior to my duty shift but not security posts allow it.