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George Floyd's death is why Kaepernick knelt, LeBron James says: 'Do you understand now?'

Ava DuVernay, Meek Mill and others also commented on Floyd's death in Minneapolis police custody. "You deserved your breath," DuVernay said. "You deserve ... our action."

The death of George Floyd, a black man, while in custody of Minneapolis police prompted celebrities such as NBA star LeBron James, director Ava DuVernay and rapper Meek Mill to express their outrage on social media.

James posted a photo of an officer kneeling on Floyd's neck next to a picture of former NFL player Colin Kaepernick kneeling on the sidelines during the national anthem at a game.

"This is why," the image was titled in an apparent reference to the heated controversy over Kaepernick's silent protests against police brutality and racism during the 2016 season.

"Do you understand NOW!!??!!?? Or is it still blurred to you??" James wrote in the caption.

Full coverage of George Floyd's death and protests around the country

Floyd died Monday after a white Minneapolis police officer pressed his knee onto his neck for at least eight minutes while Floyd repeatedly said he could not breathe. The incident was captured on video.

"Please, please, please, I can't breathe," Floyd begged. "My stomach hurts. My neck hurts. Please, please. I can't breathe."

Rapper Snoop Dogg posted the same images of Floyd and Kaepernick, writing: "no justice just us."

George Floyd.Courtesy photo

DuVernay posted a lengthy message on Twitter that appeared to be addressed to Floyd. "You deserved your breath, your dignity, your life. Not to die in the street, murdered by a white cop's knee on your neck. You deserve our tears, our prayers, our rage, our action. We must act — for you — and for all of those were no cameras are present."

Minneapolis police said early Tuesday that officers were responding to a report of a forgery when they tried to detain Floyd, who officers said "physically resisted." He died after "suffering medical distress," the police department said.

The four officers involved have been fired, and Minnesota Gov. Tim Walz vowed to get answers and to seek justice.

The state's Bureau of Criminal Apprehension and the FBI are both independently investigating Floyd's death. The Minneapolis Police Department said it is cooperating with the investigations.

Meek Mill said that after repeated videos of police officers "beating us like slaves" have become public, there still is no protection for black people. "Nobody haven't issued a order for the police to stop killing us! Is that not possible? Or they just saying protect yourself???" he tweeted.

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Some celebrities called for justice, while others, such as Common, tweeted the hashtag "#ICantBreathe," the words Floyd said to the officer as he was pinned to the ground.

"#BlackLivesMatter and now is the perfect time for a revolution," Chance the Rapper wrote on Twitter, writing in a second tweet: "Its gotta be an awesome privilege to be able to defend racism every day."

Rapper Cardi B wrote on Instagram: "Enough is enough! What will it take? A civil war? A new president? Violent riots?"

She added: "You don't put fear in people when you do this you just show how coward YOU ARE! And how America is really not the land of the free!"

Basketball star Isaiah Thomas said he was scared for himself and his black children. "I hope to God they don't get into some stuff and the cops come and possibly KILL them," he wrote.

DeMarcus Lawrence, a linebacker for the Dallas Cowboys, said it is hard to feel safe when minorities are being killed by the people who are meant to protect them.

"WHEN WILL MINORITIES BE FREE TO BE AMERICANS IN AMERICA!?" he tweeted.

Steve Kerr, coach of the NBA's Golden State Warriors, called Floyd's death a murder. "Seriously, what the hell is wrong with US????" Kerr, who is white, wrote on Twitter.

Actress Debra Messing said the video "f---ed me up," while Justin Bieber called for racism to end.

"THIS MUST STOP. This makes me absolutely sick," he wrote in part on Instagram.