Erica Garner, whose father died after being put in a police chokehold in a case that helped spark the Black Lives Matter movement, has died in New York.
The 27-year-old Ms Garner suffered a heart attack triggered by an asthma attack a week ago, and had been put in a medically induced coma, according to The New York Times.
Her Twitter account, run by her family and friends since she became ill, asked that she be remembered as a mother, daughter, sister and aunt with a heart "bigger than the world."
Ms Garner became an activist against police brutality after the July 2014 death of her father, Eric Garner.
Mr Garner, a 43-year-old father of six, died while New York City officers attempted to arrest him on suspicion of selling loose cigarettes. One officer subdued him with a chokehold.
Mr Garner also suffered from asthma. His last words, "I can't breathe," became a slogan for activists during protests across the US in 2014 against police brutality, particularly against black people.
Ms Garner often wore clothing emblazoned with the phrase.
"She was a warrior to the end. She stood up for justice for her father," the Reverend Al Sharpton said in announcing her death at a New York hospital.
Ms Garner had given birth four months ago to a son, named after her father. He also had an eight-year-old daughter, reports said.
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The New York Police Department has banned the use of chokeholds on suspects for more than two decades.
However, it decided against indicting Daniel Pantaleo, the white officer who sought to subdue Mr Garner, in a move that sparked criticism.