Police have told our reporter Ria Chatterjee that the three boys - 19 year old twins who were in the back seat and their 22 year old brother who was in the front - had parked the car to go into a local shop when 2 men approached.
They had a short conversation before the 2 men fired three rounds into the car, killing Joseph, and leaving his older brother in a stable but critical condition in hospital. Joseph's twin managed to escape unhurt.
Detective Superintendent Gordon Allison of Operation Trident, which tackles gang-related crime, said: "As far as we're concerned, this looks like a tragic case of mistaken identity."
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The family of a father-of-three from East Ham have made a fresh appeal to catch his killer 20 years after he was murdered.
The Metropolitan Police has paid £45,000 in damages in an out-of-court settlement following the 'unlawful arrest' of a black motorist.
John Cantlie, who worked for a number of Fleet Street newspapers, is thought to have been taken hostage in November 2012.