In the wake of a grand jury deciding not to indict an NYPD officer in the chokehold death of Eric Garner, New York City Mayor Bill de Blasio invoked a phrase that has become a rallying cry on social media and protests across the country in recent months.

“You’ve heard it in so many places, people of all backgrounds, utter the same, basic phrase. They’ve said ‘black lives matter.’ They said it because it has to be said. de Blasio said in a press conference Wednesday afternoon. “Our history, sadly requires us to say that black lives matter.”

The mayor also addressed conversations he has had with his son, who is black

Because Chirlane and I have had to talk to Dante for years about the dangers that he may face. A good young man, law-abiding young man who would never think to do anything wrong. And yet, because of a history that still hangs over us, the dangers he may face, we’ve had to literally train him—as families have all over this city for decades—in how to take special care in any encounter he has with the police officers who are there to protect him.

The Justice Department says it will investigate Garner’s death.

Earlier Wednesday, de Blasio urged protesters to be peaceful on a “deeply emotional day” in a statement –

“This is a deeply emotional day – for the Garner Family, and all New Yorkers. His death was a terrible tragedy that no family should have to endure. This is a subject that is never far from my family’s minds – or our hearts. And Eric Garner’s death put a spotlight on police-community relations and civil rights – some of most critical issues our nation faces today.

“Today’s outcome is one that many in our city did not want. Yet New York City owns a proud and powerful tradition of expressing ourselves through non-violent protest. We trust that those unhappy with today’s grand jury decision will make their views known in the same peaceful, constructive way. We all agree that demonstrations and free speech are valuable contributions to debate, and that violence and disorder are not only wrong – but hurt the critically important goals we are trying to achieve together.

Read his full statement here.

This post will be updated with video and more comments from his address as they become available.

This is a developing story. Check back for more information soon.