YET another white police officer won’t face criminal charges after fatally shooting an unarmed black man, US prosecutors declared on Monday.

Former Milwaukee police officer Christopher Manney, who was sacked after he shot dead Dontre Hamilton in April, won’t be charged because he shot in self-defence, legal authorities said.

The controversial decision prompted the US Department of Justice to announce a federal investigation of the case.

Mr Manney is at least the third white police officer to avoid charges in the past month after a confrontation that led to a black man’s death, including cases in Ferguson and New York City.

“Manney’s use of force was privileged and justified,” claimed Milwaukee County district attorney John Chisholm.

After waiting eight months for the decision, Mr Hamilton’s family reacted with disappointment and anger. Their attorneys called for a federal investigation and Mr Hamilton’s brother Nate said the family had “cried too long.”

“We need to stop the violence in our communities so we can get rid of these pigs that kill us,” he said to shouts and applause. “Because that’s what they are. They feed off of us. And we can’t let them do that no more.”

Hamilton family lawyer Jon Safran later said Nate Hamilton doesn’t condone “any type of violence” and the family was dealing with “great anxiety and frustration.”

Mr Hamilton’s family said that Dontre had suffered from schizophrenia and had stopped taking his medication.

The family has led protests in the months since his death.

They took to the streets again on Monday afternoon, with Nate Hamilton leading a crowd as it marched through intersections chanting “arrest the police.”

The group eventually dispersed without incident.

Later on Monday evening, more protesters gathered in the rain at the park where the shooting occurred.

Hours after Mr Chisholm’s announcement, US Attorney James Santelle said the Department of Justice, along with his office and the FBI, would review whether there had been any violation of federal civil rights law.

In New York, Mayor Bill de Blasio pleaded for a pause in protests until after the funerals of two slain police officers.