A Florida woman walked into Walmart and allegedly built a homemade bomb. An off-duty cop and a security guard stopped her before she could set it off.

A Florida woman who walked into a Walmart and attempted to construct a homemade bomb was stopped just in the nick of time, police say.

Emily Stallard, 37, was spotted wandering around a local Walmart gathering supplies with her son when a security guard took notice of her suspicious behavior, WTVT-TV reported.

After the guard watched Stallard open several unpurchased items, including "flammable materials, projectiles, and matches," he decided to call the Hillsborough County Sheriff's office and alert an off-duty Fish and Wildlife Conservation officer who happened to be inside the store.

According to the police report, the off-duty officer and security guard stopped her right as she was about to light her shoelace as a wick. The two men then detained Stallard until deputies arrived.

The deputies found a mason jar with fuel denatured alcohol and wire brad nails inside.

"This woman had all the supplies she needed to cause mass destruction at her disposal," Sheriff Chad Chronister said, according to WTVT-TV.

"Had it not been for an alert off-duty law enforcement officer and a watchful security staff at Walmart, she may have followed through with her plans to cause an explosion inside the store. I can't stress this enough: if you see something, say something. You don't have to tackle a bad guy to be a hero," he added.

Investigators said that Stallard had also taken her young son into the store with her, enlisting his help in making the bomb.

"The defendant encouraged the child to engage in an act that could have caused great bodily harm and induced the child to become delinquent," the arrest report said.

Investigators added that Stallard resisted arrest and spit at deputies as she was being loaded into a patrol car.

She has been charged with multiple felony crimes, including attempted arson, fire bombing, and child abuse.