Two doctors who carried out an independent autopsy of George Floyd, the black man whose death in Minneapolis police custody last week triggered nationwide protests, said on Monday that he died from asphyxiation and that his death was a homicide.

The doctors also said Floyd had no underlying medical conditions that contributed to his death.

That contradicts the initial findings of the official autopsy by the Hennepin County Medical Examiner.

It said there was no evidence of “traumatic” strangulation and also said coronary artery disease and hypertension also likely contributed to his death.

The county’s full autopsy report has not yet been released.

“The evidence is consistent with mechanical asphyxia as cause of death and homicide as manner of death,” said Dr. Allecia Wilson, one of the two doctors who performed an independent autopsy, who is the director of autopsy and forensic services at the University of Michigan.

Dr. Michael Baden, who also took part in the independent autopsy at the behest of Floyd’s family, said he agreed with Wilson’s findings and that the death was a homicide.

Baden added that “the autopsy shows that Mr. Floyd had no underlying medical problems that caused or contributed to his death.”

Baden has worked on several high-profile cases, including the 2014 death of Eric Garner, a black man who died after being choked by police in New York City.

It was not just the knee to Floyd’s neck that killed him, Baden said, but also the pressure that two other officers were applying to Floyd’s back that cut off oxygen from flowing in or out of his lungs.

Attorney Ben Crump, who is representing Floyd’s family, said the family wants first-degree murder charges lodged against all four officers who were at the scene – and they want the violent protests that has wracked the United States to end.

“George died because he needed a breath, a breath of air,”Crump said. “I implore you all to join his family in taking a breath – taking a breath for justice, taking a breath for peace, taking a breath for our country and more importantly taking a breath for George.”