Detectives are hunting three killers who stole their victim's car after stabbing him to death.
Darryl McClymont, who was 23, was murdered early on Sunday in Isleworth in west London.
The details now from Margaret Feord.
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Passengers looked horrified as the girl took the potentially lethal shortcut between platforms.
Police were called to Kilburn High Road at 5.20pm after reports of a shooting.
In just 24 hours the offer was retweeted more than a thousand times on Twitter.