A medical examiner on Monday classified American man George Floyd’s death as a homicide, AP reported. Floyd, an African-American man, had died on May 26 in Minneapolis, Minnesota, after being assaulted by a police officer.

“Decedent experienced a cardiopulmonary arrest while being restrained by law enforcement officer,” the report said. The examiner said Floyd suffered from heart disease and hypertension, and listed fentanyl intoxication and recent methamphetamine use.

On May 26, Derek Chauvin, a white man and former Minneapolis police officer, and three other officials detained Floyd after he had allegedly used a counterfeit bill at a store. Outrage grew after a widely shared video showed Chauvin kneeling for almost nine minutes on Floyd’s neck. Floyd was seen gasping for breath, pleading with the officials saying, “I can’t breathe”, and died on the spot. While all four officers were fired last week, Chauvin was arrested and charged with third-degree murder and manslaughter.

Floyd’s death sparked widespread outrage and protests across cities in the US. Hundreds of people on Friday rallied outside the White House, which was briefly put under lockdown with entry and exits being shut. Crowds gathered near the White House and shouted “I can’t breathe”. Secret service agents and law enforcement officers found it difficult to contain the crowd. The protests escalated further on Sunday with the police firing tear gas to disperse the 1,000-plus crowd. Protestors also lit fire on piled up road signs and plastic barriers.

An autopsy commissioned for Floyd’s family found that he died of asphyxiation due to neck and back compression. The autopsy showed that the compression cut off blood to Floyd’s brain, and that the pressure of other officers’ knees on his back made it impossible for him to breathe, his attorney Ben Crump said.

Though a third-degree murder charge has been filed against Chauvin, Crump demanded that this be upgraded to first-degree murder. But the official autopsy of Floyd’s body said that while he faced the effects of being restrained, there was no evidence “to support a diagnosis of traumatic asphyxia or strangulation.”

At least 4,400 people have been arrested in the United States over the past few days for offences such as stealing, blocking highways and breaking curfew, during protests against Floyd’s death, AP reported.

Floyd’s brother, Terrence Floyd, on Monday appealed for peace at the site where the homicide took place. “Let’s switch it up ya’ll. Let’s switch it up. Do this peacefully, please,” Terrence Floyd said. Terrence Floyd said violence will not bring his brother back to life.

The crowd chanted: “What’s his name? George Floyd! and One down, three to go!” in reference to the four police officers involved in the incident who have been fired from their jobs. Only Chauvin has been arrested, while the protestors demand the arrests of all four.

United States President Donald Trump, who barricaded himself in a secret underground bunker on Monday during protests outside the White House, called himself the “president of law and order” and threatened to deploy the United States military to American cities to quell protests. Trump said he would mobilize “thousands and thousands” of soldiers to keep the peace if state governors did not use the National Guard to take the sting out of the protests.

Federal troops are barred from making domestic arrests seizing property or searching people, under a law formulated in the 1800s. However, under extreme circumstances, the president can invoke the Insurrection Act, which allows National Guard troops to be used for law enforcement.