When you are a criminal, everyone you see is a potential target. However, when thinking like a criminal, you must also weigh the risk versus the benefits when it comes to picking your victims. For robbers, knowing that a person may be armed in an environment is usually a very big target. After all, everyone likes a defenseless victim that cannot retaliate.
They say Grand Theft Auto perpetrated crime. However, in those games, it was always a bad idea to rob a gun store. This is because more likely than not, the owners and employees are always packing heat. A gun store should be one of the last places you try to rob, because it actually might be your last.