The family of Chris Kaba, who was shot dead by an armed Metropolitan Police officer in south London on Monday, said the firearms officer involved should be “immediately suspended”.

The demand came as hundreds of demonstrators gathered in central London to protest against the fatal shooting of the 24-year-old.

The Independent Office for Police Conduct (IOPC) has launched a homicide investigation into the incident involving the Metropolitan Police (MPS) in Streatham Hill, but the family said they were “shocked” the decision to do so was only made on Friday.

In a statement issued on their behalf, Daniel Machover, head of civil litigation at solicitors Hickman & Rose, said: “Following a police stop in Streatham, south-west London, shortly after 10pm on Monday September 5, a firearms officer employed by the MPS fired a fatal shot at Chris Kaba while he was seated, unarmed, in a car.

“On being notified of the death of Chris Kaba, the IOPC should have immediately opened a homicide and disciplinary investigation. The family was shocked to learn on Wednesday, September 7, that the IOPC had still not done so and demanded a change of heart without delay.

“The family therefore welcome the IOPC’s decisions on Friday, September 9, to open homicide and disciplinary investigations against that firearms officer, however belatedly.

“The family now await the outcome of that investigation, but seek a charging decision in this case in weeks or a few months, not years.

“Public confidence in the police and our justice system requires the IOPC and CPS to find a way to make decisions in this case on a timescale that delivers justice to all concerned. Avoidable delay is unacceptable.

“In the meantime, the family demand that the Commissioner of Police of the Metropolis immediately suspend the firearms officer, pending the outcome of the investigation.”

The crowds marching to Scotland Yard paid tribute to Mr Kaba, who was due to become a father in months.

Signs reading “Black Lives Matter”, “Justice for Chris Kaba” and “Abolish the Met” were held up as speakers using a megaphone led chants of “no justice, no peace” and “police are the murderers”.

There was a limited police presence as demonstrators assembled on Parliament Square and made their way through Whitehall.

The IOPC has previously confirmed that no gun was found in the Audi that Mr Kaba was driving.

The PA news agency understands the only firearm recovered from the scene was the one involved in the shooting.

Mr Kaba died after his car was hemmed in by two police vehicles in narrow residential street Kirkstall Gardens and one round was fired from a police weapon.

He was given first aid by officers at the scene and taken to hospital where he died later in the night.

His family, in a statement issued on Wednesday, questioned whether his life would have been “cut short” if he were not black and demanded “answers and accountability”.

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