New York's attorney general announced Saturday she would form a grand jury to probe the death of a black man .
Daniel Prude's family said he died on 30 March after being removed from life support, seven days after his detention by police in the city of Rochester.
He is the latest African-American to die after an encounter with law enforcement, cases that have galvanised protests around the United States.
The grand jury represents a bolstering of the authorities' response to Mr Prude's death as the panel has the power to issue indictments.
"The Prude family and the Rochester community have been through great pain and anguish," New York state Attorney General Letitia James said in a statement.
"My office will immediately move to empanel a grand jury as part of our exhaustive investigation into this matter."
The announcement came the day after protesters, some wearing helmets and carrying shields, clashed with police during a demonstration in Rochester sparked by Mr Prude's death.
"I applaud @NewYorkStateAG for taking swift, decisive action in empaneling a grand jury - justice delayed is justice denied and the people of New York deserve the truth," Governor Andrew Cuomo said on Twitter.
Mr Prude's family and activists made his death public Wednesday, after receiving body cam footage through an open records request.
Joe Prude told journalists he had called police 23 March as his brother suffered a mental health episode.
"I placed a phone call for my brother to get help, not to get lynched," Joe Prude said Wednesday.
When officers arrived, Daniel Prude was unarmed and naked in the road, according to the video.
Police ordered an initially compliant Daniel Prude to get on the ground, but after being handcuffed he became increasingly agitated.
Officers then put a "spit hood" on him and forced his head to the pavement. Moments later he lost consciousness.
He died in a hospital a week later, when life support was switched off.
Local media said an autopsy ruled the death a homicide caused by "complications of asphyxia in the setting of physical restraint."
