Cops said in a news release that the incident happened about 11:30 a.m. May 26 at the RaceTrac at 5191 South Cobb Drive.
The mother was on the passenger side pumping gas when 17-year-old Michael Tyrek Williams got in the car by "sliding" into the driver's seat, according to police.
He drove off with the child in the back seat and ditched the vehicle nearby, police said. The child was not harmed.
Williams is expected to be charged as an adult, according to a district attorney’s office spokeswoman.
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Cops said Williams, who lives just south of the former Turner Field site in Atlanta, was arrested on felony charges of kidnapping, hijacking a motor vehicle and theft.
Something similar happened to a toddler in Midtown in November. And in south Fulton County, the vehicles of actress Queen Latifah and retired Superior Court judge Marvin Arrington Sr. separately got nabbed.
Cops refer to these gas station vehicle crimes as "slider thefts."
Cobb police reminded people to not leave valuables visible in their vehicles, as that could attract criminals — even while pumping gas for a minute or two.