When Mr Richards continues to move his motorised wheelchair away, Mr Remington opens fire with nine bullets, hitting the suspected shoplifter in the back and the side.
Mr Richards then falls out of his wheelchair onto the ground.
Shop CCTV footage shows him lying on the pavement, bleeding out, as he is handcuffed by the officer.
Tucson police chief Chris Magnus said Mr Remington had been called to help by a Walmart employee.
“According to the employee, he caught up with Mr Richards outside as he fled the store and asked to see a receipt for the toolbox,” CNN quoted Mr Magnus as saying.
“Instead of providing the receipt, Mr Richards brandished a knife and said, ‘Here’s your receipt.'”
Mr Magnus told a press conference he was “deeply disturbed” by his officer’s actions.
“His use of deadly force in this incident is a clear violation of department policy and directly contradicts multiple aspects of our use of force and training.
“As a result, the department moved earlier today to terminate Officer Remington.”
Tucson Mayor Regina Romero said Mr Remington’s actions were “unconscionable and indefensible.”
“It is moments like this that test our resolve to ensure justice and accountability,” she was quoted as saying by CNN.
“We owe this to all Tucsonans. I ask our community to remain calm and be patient as investigations ensue.”
An attorney for Mr Remington has been widely quoted by US media as saying the video did not tell the whole story of the shooting.
“Many more important details were withheld” from the police department’s news conference, Michael Storie told the BBC.
The shooting is the latest in a country where law enforcement has been shown to readily resort to deadly force when confronting criminal suspects.
There is no official national record of fatal shootings by US police officers, and reporting of incidents by police departments is voluntary.
A tally by the Washington Post published Wednesday shows more than 900 people have been shot and killed by police in the last year.
Additional reporting by Evan Young.
#policeman #fired #fatally #shooting #man #wheelchair #times