Derek Chauvin, the Minneapolis officer who knelt on arrested man George Floyd's neck to the point he could not breathe before dying, has been charged with murder.

Floyd's death was captured on video.

He was seen struggling for air and begging officers to get off him so he could breathe.

His death sparked days of unrest across the country to protest the police killings of unarmed black men.

Hennepin County Attorney Mike Freeman said "we felt it appropriate to focus on the most dangerous perpetrator", referring to an investigation that is ongoing and which has included the other officers at the scene.

Freeman said Chauvin was charged with third-degree murder and manslaughter.

A criminal complaint was only expected later in the day when he made these charges known to the media.

Additional charges may be possible.

The three other officers remain under investigation.

They too were caught on video during the fatal arrest.

Freeman said they too will face charges.

All four officers have since been fired.

Did not act fast enough

Freeman also said the arrest and charges announced Friday were done "as quickly as evidence has been presented to us".

Criticism piled on as Chauvin remained free after Floyd died on Monday.

Minneapolis Mayor Jacob Frey called for Chauvin's arrest after the video went viral.

Frey asked during a news conference earlier this week: "Why is the man who killed George Floyd not in jail?"

Police chiefs across the country have condemned the officer's tactic of pinning his knee into Floyd's neck during the arrest.

The violent arrest has led to independent investigations by the FBI, as well as Minnesota Bureau of Criminal Apprehension, and the Hennepin County Attorney.

Chauvin is in custody of Minnesota's Bureau of Criminal Apprehension.

Chauvin is a veteran of the department with 19 years of service.

He began his career at the Minneapolis Police Academy in 2001.

He has been involved in three officer-involved shootings in his career, including one that turned deadly.