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LAND O' LAKES — Vernon Messier fell to the floor, yelling as he saw blood.

A bullet had gone clean through his right leg. But as he looked around the Publix check-out lane on Sunday, there was no assailant to be seen — and no gun.

Nobody else in the store saw what happened, either.

It would take deputies a while to figure it out who did it, and how.

Sheriff's documents obtained by the Tampa Bay Times reveal new details about the bizarre shooting that unfolded at the Publix at 2121 Collier Parkway. It was one of several recent incidents in which guns were inadvertently fired in public across the bay area, including an instance where a construction worker fatally shot a coworker in Riverview.

The couple involved in the Publix incident, Vernon and Lillian Messier, did not respond to multiple attempts for comment. But documents and video released by the Pasco County Sheriff's Office describe the moments leading up to the shooting, the aftermath and how deputies figured out what happened.

• • •

The story starts just before 1 p.m. Sunday. The Messiers were in aisle no. 11 at the front of the store. The husband, 69, was standing in front of a credit-card keypad, deputies said. Meanwhile, his wife was loading groceries into a shopping cart as they were being rung up.

What followed was captured by the store's video surveillance system and described by deputies:

As Lillian Messier, 66, moved some toilet paper into her cart, she knocked over her small, brown purse, which she had set on the counter next to the keypad.

The purse landed to the right of her husband. That's when employees and shoppers told deputies they heard a loud pop, smelled gunpowder — and saw Vernon Messier drop to the floor.

"I've been shot," he called out, according to a shopper standing in line behind him.

Onlookers rushed over to help.

The 18-year-old cashier, Sabrina Diaz, told deputies she saw two wounds near Vernon Messier's shin and grabbed paper towels to help the bleeding man.

The store's meat manager, Stuart Reagan, 35, went looking for bandages and a first-aid kit.

Dr. Timothy Balling, a 53-year-old emergency room physician, walked into the store, learned what happened and starting treating the wounded man.

Where was the wife? The store video showed Lillian Messier picking something off the floor, putting it in her cart, and leaving the store for about two minutes, deputies say.

She later told deputes that she ran out to the car with their groceries because the couples' cell phones were there. But no one answered when she called 911, so she ran back into the store and saw her husband being treated.

But there was no gun visible in the video. It showed nothing of "significance," a deputy wrote.

• • •

A deputy arrived at the store, his bodycam recording. Save for the bleeding man sitting on the floor, everything seemed normal inside Publix.

Vernon Messier was baffled.

"Don't even ask me what happened. I have no idea," he said. "I heard a gunshot and I fell."

Messier said he didn't see a gun or anything suspicious. He thought the gunshot might have been fired through the glass doors. The deputy asked him if he had a gun.

"No, I don't have one or it would have shot me in the ass," Messier said, laughing.

The doctor told a deputy the bullet was a "through-and-through injury," a report said. That's a forensic term meaning the bullet left an entry and exit wound. The doctor told the deputy that he wrapped the man's wounds tightly.

The deputy looked for evidence on the floor as people stood in line waiting to pay for their stuff. It was a crime scene, after all.

Paramedics took Vernon Messier to St. Joseph's Hospital in Tampa.

• • •

How did deputies solve the mystery? Lillian Messier was the key.

Later that day, deputies said, she revealed that her husband had been shot by the Cobra Firearms Derringer .38 special she kept in her purse. The gun fired when she accidentally knocked her purse off the counter. She and her husband both have concealed carry permits.

The wife invited a deputy to the couple's camper in Land O' Lakes, the report says, and let them search the purse, a Fossil handbag with a strap. She said she was afraid to touch it because she feared the gun might fire again.

The deputy found the chrome .38 pistol in the purse, a report says; inside the gun was a spent shell casing and a fresh round.

The gun had no trigger guard and was buried loose, unholstered, under several items, a deputy noted in the report.

The wife said she was afraid she'd be arrested. But the report explained why she faces no charges.

"Lillian's actions did not have intent to cause harm to her husband," the deputy wrote.

The case was classified as an "accidental injury" and closed.

Times senior researcher Caryn Baird contributed to this report. Contact Justin Trombly at jtrombly@tampabay.com. Follow @JustinTrombly.