Ventura Santos Mateo, 60, was in his garage teaching a friend how to clean his gun.
Investigators said he was holding a Sig Sauer pistol above his waist when the weapon discharged in the direction of the street, striking the girl in her right upper arm. The 12-year-old was riding in the front seat of the car, with her younger brother in the back seat. Her father didn't realize she had been shot until he pulled into his driveway about a block down the street.
"Surprised and distressed by the inadvertent shot, Mateo 'nervously' shot again by accident, striking himself in the left thigh," the Sentinel reported, citing police.
Both he and the girl are expected to recover from the injuries. A police report said he won't be charged, but authorities are still investigating the incident.