The sign appears to be part of a superhero-themed marketing campaign that is not related to guns. (Thomas Johnson/The Washington Post)

Walmart is apologizing after a photo of a back-to-school sign over a glass firearms display in one of its stores rocketed across social media.

“Own the school year like a hero,” the Walmart sign read.

One Twitter user had a simple question for Walmart, the largest retailer of firearms and ammunition in the United States: “What are you suggesting?”

The sign appears to be part of an ongoing superhero-themed marketing campaign that is not related to guns.

The photo appeared to create confusion within the company, whose explanation for the store’s location was at odds with a woman claiming to have seen and photographed the display.

Charles Crowson, a spokesman for Walmart, told The Washington Post that the chain’s operations team is working to identify the store in question, which involves looking for what the company is calling “patient zero” — the first photo of the display.

Crowson said the display and the configuration of the store suggest the photo is legitimate. It was not clear whether the sign was placed there by an employee or a shopper.

“What’s seen in this photograph would never be acceptable in our stores,” he said in a statement. “We regret this situation and are looking into how it could have happened.” He declined to comment on the connection critics were making between guns and mass shootings on school campuses.

Crowson said early indications that the sign was at a store in Evansville, Ind., were incorrect.

But Leeanna May, who told The Post she took the photo, insisted it was true.

May said she was in Evansville on an early-morning shopping trip Wednesday with her husband when they walked by the sporting goods section, where May spotted what she called a “disgusting” display.

“We have already lost so many innocent lives to guns,” she said, adding that she drew an immediate connection between firearms and school shootings. May said she alerted store employees but could not find a manager.

“People don’t seem to honestly care,” she said.

Walmart’s Twitter account replied to dozens of angry comments about the photo. In what appears to be the first reply over the incident, the company tweeted May, whose account is now private, at 8:17 a.m. Wednesday morning to ask the location of the store.

After May said that the store was in Evansville, the company replied at 9:33 a.m. to say: “I’m happy to tell you our store manager Christina has removed the sign from the display. Thanks again for alerting us to this.”

Crowson reiterated Wednesday that the company does not believe this sign was at the Evansville store after a review of photographs and surveillance video, which concluded the configuration of the sporting goods section was “not consistent” with the photo.

The display is yet another marketing-related mishap for the megachain.

In July, Walmart was blasted for using a racist term to describe a wig cap sold on its online store. The third-party item’s color was listed as “n—– brown.”

Walmart also drew fire ahead of Sept. 11 last year, when a Panama City Beach, Fla., store used Coca-Cola products to build an American flag display with two black towers, signifying the World Trade Center under a banner image of the New York skyline with a message “WE WILL NEVER FORGET.”

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