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An eyewitness has told BBC News that she was walking in the Streatham area towards a pub when she was approached by another woman "in distress".

Emma, from Streatham, said: "She was shouting her head off saying 'don’t go any further, he has stabbed this woman with a knife, he stabbed her in the back.'

"We then saw a woman half sitting, half lying on the floor with people around her but no ambulances or anything.

"About 30 seconds before that a dark car sped past us and we looked ahead up the road realising that it was police in plain clothes, which the woman was pointing to and shouting ‘that’s the police they’ve shot the guy'."

She added: "The distressed woman who stopped us kept pointing at that injured lady and saying 'he came in the shop, grabbed a knife, pulled out a knife and walked out on the street and just stabbed that lady'."