When the video starts, the woman appears to be in the middle of a sentence and is speaking calmly to barista Alex Beckom, who is Black. "When you talk to me like that, I know it's because you're discriminating against me because I'm a Trump supporter," the customer says. "F--- Black Lives Matter. I need a straw."
Beckom, 19, gives her a straw: "Here you are."
"Thank you," the customer says. "And I need sugar, too, please, the raw sugar, like, two packets, please."
As Beckom fetches packets of sugar for the customer, she says: "The next time you come in, I need you to keep a mask on."
"Its not a law," the customer says, her voice growing louder.
"It's a hoax, I don't have to wear a mask, I'm not going to wear a mask," she shouts. "This is America. I don't have to do what you say! Trump 2020!"
"You need to leave, thank you" Beckom says.
The woman starts to walk out of the store, but spins around and shouts back through the slightly ajar door: "F--- Black Lives Matter!"
NBC News does not know what occurred before the events shown in the video.
NBC San Diego reported that the customer reportedly had pulled down her mask to speak to another barista.
Beckom told the station that when she asked the woman to keep the mask on in the store, she complied at first, but then pulled it down once more.
“I’m Black in America, so I’ve dealt with these kinds of situations before, so I am able to stay calm and collected in these types of situations because I don't want to risk my job," she said.
"Even the president got [Covid-19], so I don't understand how now it's something that's turned into such a them or me situation when it should be everyone coming together to make sure we all don't get sick or get hurt," Beckom said.
In a statement, a Starbucks spokesperson said, "This behavior is not welcome in our stores.
"Our focus right now is providing support to our partner who demonstrated tremendous composure during a very difficult interaction."
This article was originally published on NBCNews.com.