Washington (CNN) A Republican candidate for Kentucky secretary of state has apologized after suggesting he'd like to use US Rep. John Yarmuth as target practice.

"I'm so proud of my @NRA rating, I'll wear it on my chest," Yarmuth, a Kentucky Democrat, posted on Twitter Monday, along with a picture of him wearing a "F" pin showing his rating from the National Rifle Association.

I'm so proud of my @NRA rating, I'll wear it on my chest. I invite my colleagues to join me in wearing our F ratings every day until the GOP finally stands up to the gun lobby and helps us pass common sense gun safety legislation. Find me to get a pin. #MarchForOurLives pic.twitter.com/sOECS54QOK — Rep. John Yarmuth (@RepJohnYarmuth) March 19, 2018

Carl Nett, whose campaign website says he's a former US Secret Service agent and CIA contractor, replied that Yarmuth should move the pin "over just a bit."

"I was trained center mass," he added, referring to the law enforcement tactic to hit a suspect's vital organs. Nett has since deleted the tweet.

After receiving backlash from Democrats and Republicans in his state, Nett later apologized on Twitter.

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