The shooting, which occurred about 9:50 p.m. Saturday, wounded the 3-year-old boy in his lower abdomen.
His mother, Lisa Evans, 22, had left the Kel Tec .380 handgun unattended and thought her son was eating in another room of their Clarksville, Tenn., home, police said. As she sat with her back to the sofa, working on a computer, she heard the gun go off and turned to find her son crying and clutching his stomach, investigators said.
The boy was flown by helicopter to Vanderbilt University Medical Center where he underwent emergency surgery, Gannett Tennessee reported.
Evans has a carrying permit for the gun. Police said charges were pending.