Do you think wearing on-body cameras on duty should be mandatory?
With 42 states now allowing civilians to carry concealed firearms, there is a good chance this man is acting within the law. You will encounter, civilians legally carrying concealed firearms more often today than ever before. How you should respond is largely determined by the behavior of the civilian and the laws in your state.
If you're lucky enough to have an eyewitness to a crime, and your investigation leads to a possible perpetrator, getting a photo ID is often the next logical step. As with everything else you do, there's the wrong way and the court's way.