A surveillance camera captured the entire attack. Police say the incident started when the woman tried, unsuccessfully, to return merchandise.
The reaction to the woman nearly running over children is universally surprising.
Union City police want to find the driver who narrowly missed a 3-year-old and her mother.
"She intentionally backed up twice to get out of that parking lot," said Sgt. Steven Mendez. "So we're calling it an assault with a deadly weapon."
Police say the rage was sparked when Walmart denied the woman's attempt to return batteries to the store around 6 p.m. Sunday night.
"As she started pulling out, actually, the family members were saying that she was yelling and screaming something in her car, and was pounding her fists against the steering wheel," Mendez told ABC7 News.
The parking lot is covered in cameras, but police don't have a clear shot of the license plate.
"So, if people have video or they have a picture of the license plate, or the suspect that we could use to help us out a little bit," Mendez said.
"You already have a lot to worry about and then someone is trying to kill you and your kid, that's scary," said a woman named Lilly from Union City.
The young woman was wearing a superhero sweatshirt at the time of the incident.