If a police officer is on duty, he should be allowed to carry his weapon at all times. There are several reasons for this. If there were an event to occur in the store, how could the office protect the public if his weapon were in his car? Also, if he were to leave his weapon in his vehicle, it would encourage the possible theft of said weapon.
Conceal carry and open carry are legal in many states. To infringe on this can be unconstitutional. Police officers should not be limited in this aspect like citizens are. Depending on the circumstances, the officer should not have been fired for carrying a weapon off duty while in a store.
This is another example of misplaced good intentions. If someone is legally authorized to carry a weapon and they are on duty, I don't see a problem. Meanwhile, in Miami, apparently you can not only carry your gun in baggage claim, you can pull it out and shoot people. Ridiculous.
The world would be a lot safer if more people carried guns around. People would be less interested in robbing and assaulting other people if they knew that there would be someone nearby with a weapon. That officer should have been able to take a weapon with him wherever he goes.