Patrick Lyoya was killed by a single shot to the back of his head by a Grand Rapids, Michigan police officer, an independent autopsy said Tuesday. 

Ben Crump, an attorney for the Lyoya family, said during a news conference in Detroit, Michigan that the "scientific evidence" laid out in the autopsy depicts a "horrific" killing in which Lyoya was shot by a hitherto unidentified officer while he was on the ground.

"Just another senseless killing of an unarmed Black person in America by the very individual who was supposed to protect them," said Crump, who added that Lyoya's family believes he was the victim of an "execution."

"We have to investigate whether this is another classic DWB case -- a driving while Black case -- that he profiled this Black motorist," he said.

The autopsy was carried out by Dr. Warner Spitz, 95, a prominent physician who has worked on several high-profile cases including investigations into US President John F. Kennedy's 1963 assassination and the 1968 murder of the Reverend Martin Luther King Jr.

Lyoya's death is the latest that has elicited calls against police violence and for greater racial justice in policing.

Lyoya, a 26-year-old Black man originally from the Democratic Republic of the Congo, died April 4 after an officer pulled him over in Grand Rapids.

A series of four videos released by the police department last week show Lyoya exiting the vehicle, which police said was stopped because its license plate did not match, as the officer repeatedly tells him to get back in the car.

After exiting the police car, the officer continued to tell Lyoya to get back in his car, which he did not. Lyoya is asked for his driver's license and said it is in the car and asked an unidentified person in the car a question before closing the door and appearing to walk away.

"No. No. No. Stop," says the officer, who grabs Lyoya and tells him to put his hands behind his head as a scuffle breaks out and Lyoya runs. The officer tackled him, telling him to "stop."

"Get your hands behind your back," the officer said as the struggle continues to unfold in the front yards of nearby houses. "Okay," said Lyoya.

The officer continued to appear to struggle to hold Lyoya on the ground before he broke out his taser and attempted to use it.

"Let go of the taser," the officer said after a bodycam video appeared to show Lyoya grabbing it. The bodycam deactivates during the tussle.

The cause is unclear, but three additional videos continued to capture what happened in the aftermath to varying degrees, including one by the individual in Lyoya's car.

Mobile phone footage captured by the man showed the officer and Lyoya continuing to wrest on the ground as the officer continued to tell him to "let go of the taser."

Still on top of Lyoya, who appears to be attempting to get up, the officer reached for his sidearm while continuing to tell him to "drop the taser."

A gunshot can be heard before Lyoya's body appears to lay on the ground, lifeless./aa