Newly released transcripts of the minutes leading up to George Floyd’s death reveal he told officers “I can’t breathe” more than 20 times, only to have his plea dismissed by Derek Chauvin, the white officer pressing his knee into Floyd’s neck, who said: “It takes a heck of a lot of oxygen to talk.”

Floyd’s dying words have become a rallying cry at demonstrations around the world amid a reckoning with systemic racism and police brutality. The chilling transcripts of body-camera video recordings that were made public on Wednesday provide the most detailed account yet of what happened after police apprehended Floyd on 25 May.

Before he died, Floyd cried for his dead mother and his children. “Momma, I love you. Tell my kids I love them. I’m dead,” he said.

The new evidence was made public as part of efforts by one of the officers involved, Thomas Lane, to have charges that he aided and abetted in murder thrown out.

The Congressional Black Caucus, which is made up of most of the African American members of the US Congress, on Thursday stepped up calls for legislation to be passed to reform what many believe to be largely overly militarized police forces in the US, with many departments emphasizing highly aggressive responses to crime and unrest instead of fostering community relations and investing more in social services and education.

The Georgia congressman Hank Johnson tweeted: “Systemic racism permeates too many of our police departments in this country and has existed in policing for generations.”