A Walmart gun display prodding customers to "Own the school year like a hero," was a prank, the company confirmed Saturday.

Walmart spokesman Charles Crowson told USA TODAY the company is "certain" the incident was a ruse, but offered no other details.

Walmart started its own investigation of the incident Wednesday, after a photo of the display spread across Twitter. The photo showed a glass gun case in a Walmart store with a sign on top reading, "Own the school year like a hero," the store's back-to-school slogan.

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The photo drew quick condemnation from people online and the company itself. Over a 24-hour period, the company tweeted out dozens of apologies to individual tweeters, calling the display "terrible," "definitely NOT okay" and a "regrettable situation."

Crowson didn't specify what aspect of the incident was a prank, including whether someone doctored the photo or tampered with the display.

He said the company had "several people" working on the investigation, which concluded Friday evening.

"I really don't think any retailer is immune from things like this popping up through social media," he said. "When we're faced with it, we do take the claim seriously."

@OMGItsBirdman: Explain this @Walmart