OpFam. Operational familiarity. Like this: “The guy with a gun picked the wrong clerk. How wrong? A veteran of four tours in Iraq. A 30-year military man. A former prison guard, private investigator, professional extraditor of federal prisoners and — perhaps most important on this particular Sunday night — a proud owner of a Walther PPX 9 mm handgun. Loaded, with one in the chamber, like he always carries it. Jon Lewis Alexander, 54, of Marionville [Missouri], thwarted a robbery about 9 p.m. Sunday at Beer 30 on East Logan Street in Marionville — after the would-be robber pulled his weapon first. As a store security video shows, Alexander used his left hand to push the robber’s handgun back while — in a smooth but rapid motion — pulling and swinging his 9 mm into the robber’s face. The man’s mouth, to be exact, as the robber haplessly holds his own weapon at his side. ‘One of the policemen told me later, ‘You’re a lucky man,’ ” Alexander said Monday. ‘I said, ‘I think he (the robber) is a little luckier than I am.’ ” Click here to watch the security video via news-leader.com.