On Sunday night, the Washington DC headquarters of the AFL-CIO, the nation's largest federation of unions, was set aflame. Its windows were smashed in, and a prized collection of art depicting the plight of the American worker was likely damaged. A gold inscription on its 16th Street entrance was painted over with the words "Black Lives Matter."

As the lobby burned, one Washington Post reporter tweeted that they heard bystanders urge those smashing the windows to reconsider: "No, stop! Unions are good!" and "Aw, man, not the union!"

It's unknown what the motive was, or whether there was a motive at all for burning the headquarters of the country's most influential labor organization, which represents millions of working-class people of color who are targets of police violence. But the act has raised important questions about where the AFL-CIO and other unions stand when it comes to police brutality.