(CNN) As Starbucks prepares to close its stores later this month for mandatory racial-bias training, an incident in suburban Los Angeles is showing why that training is needed.

A barista at a Starbucks in La Cañada Flintridge is accused of printing a racial slur on a Latino customer's drinks on Tuesday.

Priscilla Hernandez told CNN that a co-worker at the restaurant where she works went to the nearby Starbucks and bought drinks. It's a coffee run they make just about every day.

The co-worker ordered a white chocolate mocha and an iced caramel macchiato and told the barista his name is Pedro, Hernandez said.

But she said that when he brought back the drinks, she noticed that "beaner" was written on her drink instead of Pedro. "Beaner" is a derogatory term for Mexicans in the United States.

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