Bad idea: holding up a store clerk who happens to be proficient in firearms.

Worse idea: holding up a store clerk who is not only proficient in firearms, but who also happens to be an Iraq war veteran and a former prison guard and private investigator.

Jon Lewis Alexander, 54, is no ordinary store clerk. He has worked several “high risk” jobs and served four tours of duty in Iraq during his 30 years in the U.S. military.

And his training shows.

Video surveillance from Saturday night captures the moment a would-be thief entered the Marionville, Mo., store where Alexander works. The thief hesitates for a moment and pulls a gun — but not fast enough to dissuade Alexander from pulling his own Walther PPX 9 mm handgun and sticking it in the hapless thief’s mouth.

No one was hurt and no shots were fired.

“One of the policemen told me later, ‘You’re a lucky man,’” Alexander told News-Leader.com Monday. “I said, ‘I think he (the robber) is a little luckier than I am.’ ”