A pregnant US mother died last week after she was accidentally shot in the back by her 2-year-old son who found a loaded weapon on a nearby nightstand, police said.

Police Chief David Smith of Norwalk, Ohio, told reporters Tuesday that he was one of the officers who responded shortly after 1pm Friday after multiple calls to 911 from the woman.

The 31-year-old victim, named as Laura Ilg, told 911 operators she had been shot in the back, went into shock and couldn’t breathe, Smith said. Police found her still conscious on her bedroom floor with a Sig Sauer Micro 9mm gun resting on the nightstand.

“She explained she was 33 weeks pregnant, and her 2-year-old just accidentally shot her in the back,” Smith said.

Ilg was rushed to Fisher-Titus Medical Center for an emergency cesarean section, but doctors weren’t able to save the baby. Ilg died three hours later, authorities said.

Ilg’s husband Alek paid tribute to his wife and unborn son in a message on social media.

“If you haven’t heard, Laura and our unborn son Talisen passed away Friday. There are no words for the pain and loss I feel,” he wrote.

“She was, is, and will always be, the love of my life.”

Another family member wrote: “It’s a tragic loss for everyone. Especially their firstborn sweet boy. He is a beautiful gift to this world and we will be forever grateful he is with us. Please pray for this little family that went from almost 4 to 2 in the blink of an eye. My heart is so shocked and sad.”

Smith said the house was full of safety features, but baby gates that were usually closed had been left open. The victim was doing laundry in the bedroom, which was usually locked, and apparently didn’t realise the child had followed her before he started playing with the gun and it discharged, Smith said.

Police said a loaded shotgun and rifle were also found in the home. Smith urged families to lock up guns and never leave them loaded and unattended. No arrests have been made in the case.

“Trigger locks, gun safes, there’s a million varieties, and they aren’t that expensive. At the very least, leave them unloaded,” he said.

“Words truly cannot express how heartbreaking this is, and we cannot imagine the pain and heartache,” the department said in a statement.

- Additional reporting, NZ Herald