The encounter, which took place on Sunday in the suburban San Diego city of Santee, escalated after the barista, 19-year-old Alex Beckom, asked the White customer to put on her mask, which was hanging below her chin, Beckom told CNN.

At first, the woman complied after being asked to properly wear her mask, which had 'Trump 2020' lettered across it, Beckom said.

Shortly after, another customer at the store said the woman allegedly told the barista she did not have to wear a mask because she "had an exception." The barista said exceptions are "not a thing," according to the customer who witnessed the exchange.

While the woman's initial conversation with the barista was not recorded, video of the incident begins as the woman lowered her mask again and started yelling angrily.

"I'm not going to listen to anything you say to me when you talk to me like that," the woman said. "I know it's because you're discriminating against me because I'm a Trump supporter," she added.

The video, which has since gone viral on social media, shows the Starbucks employee calmly trying to deescalate the situation while giving the customer her beverage. The customer, however, continued to rage.

"F**k Black Lives Matter," the customer yelled while grabbing her drink from the Starbucks pickup counter.

"Again, next time you come in, I'm going to need you to keep your mask on or else I can't help you," the barista said again softly.

Video shows the customer went on angrily berating the employee as she walked out of the store yelling, "This is America and I don't have to do what you say! Trump 2020! F**k you! F**k Black Lives Matter!"

John Glaude, the customer who recorded the incident on his cell phone, told CNN he thought about intervening.

"I really wish I would have stepped in, but at the same time, I was like, I don't want to escalate the situation any further and make it more of a thing," Glaude said.

After the encounter, the barista shared a post on Facebook expressing frustration that the woman yelled "F**k Black Lives Matter."

"WTF does BLM have to do with Covid?," the barista said in the post.

CNN has attempted to identify and reach the woman seen in the video. Local authorities are not sharing her name.

Starbucks has required facial coverings since July

A Starbucks spokesperson told CNN the woman's rant was out of line and will not be tolerated. The company also said it is actively conducting an investigation to determine the appropriate next steps.

"We expect our partners and customers alike to foster a welcoming environment and this behavior is not welcome in our stores," said Jory Mendes, senior manager of corporate communications at Starbucks. "Our focus right now is providing support to our partner who we feel demonstrated tremendous composure during a very difficult interaction."

In July, Starbucks began requiring customers wear facial coverings that cover the mouth and nose while visiting all company-owned cafe locations in the United States. Customers who are not properly wearing facial coverings for medical reasons or