A 28-year-old mother leaving for work Wednesday morning accidentally ran over and killed her 2-year-old son in their driveway near Somerset.

According to Bexar County sheriff's deputies, the infant and his aunt were at the door when the infant, identified as Manny Martinez, broke free and got behind the moving pickup.

The aunt, identified as Maria Guerrero, 26, tried to run after the infant but fell, deputies said.

The mother, identified as Veronica Guerrero, didn't realize what had happened until she heard her sister screaming.

The accident happened on Senior Road near Loop 1604 at around 6:45 a.m., when it's still dark outside.