The bullet, according to investigators, struck the child in the head, near one eye.
The boy's father was downstairs with another child when he heard a gunshot.
"He was so panicked, he said he couldn't find his cellphone, and ran outside for help," Sheriff Troy Nehls said. "It was someone driving down the street, who saw him with his son in his arms screaming, who stopped and called 911."
The boy was thought to have been asleep. He apparently awakened and walked into another room, where the gun was on what the sheriff described as "a tall dresser."
Rebecca Calle said her son was another person who stopped to help.
"He saw the dad screaming, and asked to use his cell phone to call his wife," she said. "My son told me the little boy was crying and appeared to be talking and conscious. The man was frantic and scared and didn't know what to do."
It's another reminder to anyone who owns firearms to keep them locked up and away from children.
The sheriff's office is investigating the incident. The condition of the child is not yet known.