Denasia Lawrence opened her jacket just before she started to sing, revealing a “Black Lives Matter” shirt, then dropped to her left knee and performed the song. She said it was her way of protesting racial oppression.

“We’re being unjustly killed and overly criminalized,” Lawrence wrote early Saturday in a Facebook post. “I took the opportunity to sing and kneel to show that we belong in this country and that we have the right to respectfully protest injustices against us.”

Miami Heat officials said they had no advance knowledge of Lawrence’s plan to protest. Lawrence, a social worker, kept the shirt hidden until her performance.

“I didn’t get paid to sing the national anthem nor was this moment about any sort of fame,” Lawrence wrote. “Black Lives Matter is far larger than a hashtag, it’s a rallying cry.”

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The anthem issue has been a major topic in the sports world in recent months, starting with the decision by San Francisco 49ers quarterback Colin Kaepernick to not stand while it is played. Kaepernick cited racial injustice and police brutality among the reasons for his protest, and athletes from many sports—and many levels, from youth all the way to professional—have followed his lead in various ways.

Heat players and coaches stood side-by-side for the anthem prior to their game with Philadelphia, all with their arms linked as has been their custom during the preseason. The team plans to continue standing that way for the anthem this season as a show of unity.

“Throughout all of this, I think the most important thing that has come out is the very poignant, thoughtful dialogue,” Heat coach Erik Spoelstra said. “We’ve had great dialogue within our walls here and hopefully this will lead to action.”

The NBA has a rule calling for players and coaches to stand during the anthem.

“All I can say is what we’ve seen in multiple preseason games so far is our players standing for the national anthem,” NBA Commissioner Adam Silver said Friday in New York. “It would be my hope that they would continue to stand for the national anthem. I think that is the appropriate thing to do.”

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Heat guard Wayne Ellington often speaks about the need to curb gun violence, after his father was shot and killed two years ago. He had his eyes closed for most of the anthem Friday, as per his own custom, though was aware of Lawrence’s actions.

“At the end of the day, to each his own,” Ellington said. “If she feels like that’s the way she wants to stand for it, then more power to her.”

Making a statement in the manner that Lawrence did Friday is rare, but not unheard of in recent weeks.

When the Sacramento Kings played their first home preseason game earlier this month, anthem singer Leah Tysse dropped to one knee as she finished singing the song.

Tysse is white. Lawrence is black.

“I love and honor my country as deeply as anyone yet it is my responsibility as an American to speak up against injustice as it affects my fellow Americans,” Tysse wrote on Facebook. “I have sung the anthem before but this time taking a knee felt like the most patriotic thing I could do. I cannot idly stand by as black people are unlawfully profiled, harassed and killed by our law enforcement over and over and without a drop of accountability.”