Re: OH SHIT. AR15 used in Portland, OR mall shooting..
Located next to the exterior door of any indoor retail mall is a placard that gives notice of: private property, rules of the premises, and conspicuously posts words to the effect of 'no firearms or weapons allowed'.
In Oregon it is not a criminal offense to carry on private property. If you are somehow 'made', you will be asked leave and should you say anything other than "I'm very sorry about that, I did not notice the sign on my way in, please inform me where the nearest exit is such that I may leave the premises". You open yourself up to criminal trespass -> potentially a problem with your CHL. Know the laws of your state.
Public place shootings and even a Beslan style event are just one of the bad things that can happen that everyone should be mindful of every time they step outside the door. You should also think about certain potential aspects of such events when considering your training, your EDC, support gear in the vehicle, as well as emergency communications with local loved ones and friends.
Good luck