But, instead of hitting the brake pedal, accident investigators say she placed her foot on the gas pedal, sending her 1995 Nissan Altima zooming forward.
"It set her into a ‘panic mode,'" Hernandez told the AJC on Thursday. And, in an attempt to not hit the car that was directly in front of her, Anderson swerved to the right.
That's when she lost control of the car and hit 5-year-old Karla Campos as she stepped off the bus.
Anderson, 82, was not injured. She was charged with vehicular homicide and booked in the Cobb County jail Wednesday night, Hernandez said.
Anderson was not in jail Thursday afternoon. She was released late Wednesday night on a $5,000 bond, jail officials said.
Neither speed, nor alcohol or drugs were a factor in the crash, Hernandez said.
"It was driver error -- stepping on the wrong pedal and steering off the road," he said.
The case is ongoing as accident investigators are spending Thursday re-creating the scene, Hernandez said.
Karla was a student at Mountain View Elementary in east Cobb, according to Cobb County school spokesman Jay Dillon.
She loved going to the beach and was a fan of Dora the Explorer, according to her aunt, Rena Hernandez.
And she loved chocolate milk.
Karla spent weekends playing with her cousins, said Rena Hernandez, who spoke to the AJC on Thursday after a short, impromptu memorial service.
"My mother called me and let me know what happened," said Hernandez, who lives in Douglasville. "I just came running over here to see what happened."
Karla was taken to Children’s Healthcare of Atlanta at Scottish Rite Hospital, police said.
"They were going to let us see her (in the hospital)," Hernandez said. "I believed she was alive, but she was not."
Karla has two younger siblings. Martin is 3, and Daniella is an infant, born three weeks ago, Rena Hernandez said.
The accident happened around 2:45 p.m. at the intersection of Davis Road at Aberdeen Court in Marietta. The school bus, driven by 64-year-old Louis M. Smith of Marietta, was stopped and had its warning signals illuminated, police said.
Karla was let off the bus at a curb. After the Nissan Altima struck Karla, the car continued along the curb and into the grass, police said.
Her mother and two younger siblings watched the incident, he said.
"This is a horribly tragic event, and we are praying for the little girl's family," Dillon said.
Grief counselors will be at the school on Thursday, according to a message posted on the school's Web site.
Karla's aunt has three children of her own, ages 7, 5 and 3. Rena Hernandez said the families lived together at one point when Karla was younger. They also took vacations together and saw each other every weekend.
"We're so close to her," Hernandez said.
Hernandez said her 7-year-old knows that her cousin is dead. The others are too young.
"My son is expecting to see her today," Hernandez said. "He doesn't realize that she's dead."