Syrma Sotiriou was helping a customer when the preteen came in waving a weapon and demanding jewelry.
"He had a gun and pointed it at me and he said, 'Lay down on the floor.' And I didn't take him seriously because he was a kid," Sotirou said.
She grabbed the store's panic button calling an alarm company and police, and the young thief ran off. He was arrested Tuesday afternoon, according to CBS Denver.
The attempted robbery was at Sotirou's Treasured Scarab Antiques on Jan. 26.
Sotiriou is relieved police have the suspect in custody and she'd like to give him a "talking to."
"At some point along the way I probably would have smacked him upside the head if I'd gotten close enough," Sotiriou said.
Sotiriou, a grandmother of four, has owned the antique store for more than three decades, and says she wasn't about to be intimidated.
"I actually think the gun might have been a toy gun, and I'm not sure I wouldn't have tried to knock it out of his hand," she said. "I was mad. He was a kid."
Her linen hankies, her family photos, and her endless strands of antique jewelry offer her comfort, but she now has a surveillance system hooked up just in case.
"I'd just like him to say he's sorry," she said.
Police haven't publicly named the suspect.