St. Louis police have released a video of this week's fatal shooting of Kajieme Powell, just a few kilometres from Ferguson, the site of widespread protests over the police shooting of black teenager Michael Brown.

The video, taken by a witness on a mobile phone in North St. Louis, shows the rapid escalation of the incident, as two officers arrive at the scene in a police vehicle and within a few seconds fire repeatedly on Powell.

The recording, which starts just minutes before the arrival of the officers, shows the 25-year-old Powell pacing around the sidewalk outside a store where he allegedly stole soft drinks. The cans are seen placed at the edge of the curb near him.

Although he appears agitated and is heard talking to himself, Powell does not interfere with numerous passersby.

Within minutes, a police car draws up pulling onto the curb and two officers step out to the curb to confront Powell, shouting at him to get down.

Screen Shot Powell 2

A screenshot from a cell phone video shows Kajieme Powell pacing up and down the sidewalk just minutes before St. Louis police arrive at the scene.

Police say Powell was brandishing a knife, which was recovered at the scene. Although the knife is not clear in the video, he can be seen holding an object in one hand.

The video shows the officers shouting at Powell to “drop the knife.” Powell yells back, “Shoot me.”

Powell starts to walk away and steps up on to a raised grassy area near where the police car is parked. He is then seen turning around and facing the officers, and starts to walk towards them. Both policemen then draw their holstered handguns and open fire, shooting him repeatedly until he falls on to the sidewalk.

St. Louis Police Chief Sam Dotson said police released the video to address concerns over why the officers did not use less lethal means to incapacitate Powell.

Dotson suggest the officers may not have been able to use a Taser on Powell because of his sweatshirt.

In the video, Powell’s sweatshirt appears to be unzipped, with his T-shirt clearly visible. 

The death of Powell came amid several days and nights of unrest in nearby Ferguson following the death of Michael Brown, a black teenager who was shot by a police officer on Aug 9.

The 18-year-old's death has brought to light the tense relations between Ferguson's black community and the local police department and rejuvenated a heated debate over race and policing in America.