What they told me in my CCW class. You are more help to the police if you become extra vigilant. Look closely at every part of the robbers. Check for tattoo's, birthmarks, distinguishing marks of any kind. Look to see if you can compare them to objects to determine size, and height. Try to notice speech patterns or accents. When they leave, see if you can determine which way they go, to what kind and color of car, and obviously as much of a plate number as you can get. Playing hero is not your job, thats what the police are for, and you may end up getting yourself, or another innocent person harmed. If they are unorganized, they may be on drugs and incoherent, or desperate and scared, that makes them unstable, and extra dangerous. If they are organized, they're pros, and will probably either kill you with out hesitation, or be gone without trouble in mere minutes. It's only going to seem like hours, but it's only a few minutes. Thats what I would do, unless my life, or that of my wife specifically were in danger, I would not attempt to draw my weapon, and use it. Thats law enforcements job.