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President Obama comforts a woman during a remembrance ceremony in Arlington, Va. (pool/Getty Images)

(The Root) -- Today marks the 12th anniversary of the attack on the World Trade Center. Citizens across the nation and around the world marked the day with reflection and remembrance, both online and off.

On Twitter, black celebrities tweeted messages of condolences and encouragements for those still in mourning.

— SWIZZ BEATZ (@THEREALSWIZZZ) September 11, 2013
— Niecy Nash (@NiecyNash) September 11, 2013
— kerry washington (@kerrywashington) September 11, 2013

 

— Keri Hilson (@KeriHilson) September 11, 2013
— Serena Williams (@serenawilliams) September 11, 2013
— Mariah Carey (@MariahCarey) September 11, 2013
— MYA (@MISSMYA) September 11, 2013