DETROIT, MI -- Democratic presidential hopeful and New York City Mayor Bill de Blasio came under fire for his handling of an investigation into the death of Eric Garner.

Earlier this month, Attorney General William Barr announced New York police officer Daniel Pantaleo would not be prosecuted for the death of Garner, an African American man who was killed during an arrest in 2014. Garner’s death played out on cellphone screens, as bystanders recording Garner gasping “I can’t breathe" while Pantaleo allegedly held him in a choke hold prohibited by the NYPD.

Garner’s death was one among several deadly encounters between black people and police officers that sparked the Black Lives Matter movement and a national conversation on policing.

Protesters raised the issue early in Wednesday’s debate at The Fox Theatre in Detroit, interrupting multiple candidates giving their opening remarks with chants. The protesters emerged when de Blasio gave his opening statement, when scattered yells of “I can’t breathe” were audible as the debate streamed on television.

Later, during U.S. Sen. Cory Booker’s, D-N.J., speech, police came to escort out the protesters, said Rev. Kirsten John Foy, who was among them. The group began yelling again, including the phrase “fire Pantaleo."

U.S. Sen. Cory Booker, D-N.J., kicked off the discussion by evoking Garner while talking about the impact of a “broken” police system. Booker called for a national standard for when officers can use force.

“He knew what he was doing, that he was killing Eric Garner and yet he has not been brought to justice,” Booker said. “That police officer should be off the street.”

U.S. Sen. Kirsten Gillibrand, D-N.Y., said Pantaleo should be fire immediately.

“If I was the mayor I would fire him, but as president, i would make sure that we had a full investigation, that the report would be made public, and if I wasn’t satisfied we would have the consent decree," she said.

De Blasio said New York is “changing fundamentally” how it approaches policing. He said “there will never be another Eric Garner” in the city.

“I know the Garner family, they’ve gone through extraordinary pain, they are waiting for justice and they;re going to get justice, I have full confidence in that,” de Blasio said.