(CNN) A Florida woman is facing charges after she went to a Walmart in Tampa, got items from the shelves and started making an explosive device inside the store, authorities said.

Then the woman, Emily Stallard, 37, tried to detonate it in the store Saturday, the Hillsborough County Sheriff's Office said in a statement Tuesday.

"A security guard with Walmart noticed the woman ... roaming the aisles of the store and opening unpaid items. The items included flammable materials, projectiles and matches," the sheriff's office said.

The security guard called the sheriff's office and also notified an off-duty Florida Fish and Wildlife Conservation officer who was in the store at the time. The officer and the security guard stopped her just before she lit a wick and detained her until deputies arrived, CNN affiliate WFLA reported.

Deputies rushed to the scene when they got reports of a customer trying to ignite a bomb inside the store.

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