A PRO-GUN activist has been shot in the back by her four-year-old son a day after boasting about the tot’s shooting skills.

Jamie Gilt, 31, was driving in the US state of Florida on Tuesday when her son found her loaded .45 semiautomatic handgun on the floor of the pick-up truck and accidentally fired it.

The bullet ploughed through the driver’s seat and into Gilt’s back, Jacksonville.com reported. The boy, who was sitting in the back seat, was unharmed.

Just a day before the bizarre shooting, Gilt reportedly trumpeted her little boy’s gun skills on her Jamie Gilt for Gun Sense Facebook page.

“Even my 4 year old gets jacked up to target shoot with the .22,” she wrote on Monday in a heated exchange about using guns for self-defence, according to New York Daily News.

The vocal Ted Cruz supporter also argued she had the right to shoot anyone who threatened her or her family.

Gilt was on her way to pick up a pony when her son shot her.

A police officer spotted Gilt’s truck and horse trailer stopped in the middle of the road and noticed she was “behaving erratically”.

“As the deputy slowed to check on the vehicle, he observed an adult female in the driver’s seat motioning to him as if she needed assistance,” Putman County Sheriff’s office spokesman Joseph Wells said.

“The deputy ran to the vehicle and quickly determined that the driver had been shot.”

Gilt was rushed to UF Health in Gainesville and is in a stable condition.

Wells said there was a booster seat in the back of the truck, but the boy was not strapped into it.

He said the boy is in the custody of family members, adding that the Department of Children and Families has been contacted.

The shooting is being investigated as accidental and the tot will not face charges. It’s not clear if Gilt will be charged.

According to the NRA’s Institute for Legislative Action website, it is generally illegal to openly carry a weapon in Florida, but people can get permits to carry handguns.