Her 15-year-old cousin went to the store to buy some chips while they waited for help, she said.
"At first it seemed like he was trying to be friendly," she told WBBM.
Buitron told WBBM that the cashier questioned the legal status of her two cousins waiting outside.
And she says, "No, they are my cousins, they are from Mexico." And he asked, "Are they illegal?"
This part of the incident can not be seen in the videos posted on Facebook on Tuesday and quickly reached hundreds of thousands of views.
A video begins with the employee who was not identified and two women about "undocumented."
He points to his chest and says, "I'm American."
One of the women then asks, "What's your problem?"
"It's illegal," said the employee, what led to more strife.
Then he asked the woman, "Are you a citizen?"
"Yes," the woman replied, and then repeatedly asked, "What's your problem?"
Do not you know the rules?" Asked the employee. "They have to return to their country."
The quarrel got tougher and one of the women threatened to call the police.
"ICE is coming," said the clerk. "You are in the wrong country."
Dozens of people protested in front of the shop on Wednesday.
Buchany Energy, which owns the Bucky convenience store, released a statement Thursday stating that the employee is no longer working for the company.
"Over the last few hours, a video has been posted on social media that involved a Bucky & # 39; s employee in a confrontation with a customer, whose comments do not reflect Bucky & # 39; s basic values Convenience stores We are aware of the situation and take care of this staffing problem, we take this matter seriously and strive to treat all customers with respect.
"Our internal investigation has stopped the employee from working for the company. "
CNN has attempted to identify the cashier to ask for his opinion, but his former employer, Buchanan Energy, has not disclosed his information.
The mayor of Naperville, Steve Chirico, released a statement Wednesday condemning hatred in the community.
"I know that in social media, a video about one Incident that has recently taken place at a gas station in Naperville. Our police department in Naperville has reviewed the video and is reviewing it.
"Let me be very clear: hatred does not have a home here in Naperville." Frankly, this kind of behavior has no place in society as a whole. "Our city is proud of itself for being open and open to all, courtesy against each other is an important component of a global citizen, and I urge everyone in our community to demonstrate the kindness, compassion, and decency our residents are known for and our world needs more of. "
The Police Department of Naperville said they would investigate the incident.
"The Naperville Police Department has reviewed the social media video for an incident at a Naperville gas station, and we will continue to investigate the matter and monitor all related activities in Naperville."
CNN has contacted Carolina Buitron and other members of her family, but received no response.
Brad Parks of CNN has contributed to this story.