Azezur Khan, known as Ronnie, had just left the service of his school friend in East Dulwich and was making his way to the burial when he was gunned down at around 3pm.
The Metropolitan Police said he was hit a number of times in an exchange of gunfire between Rocknells Place and Forest Hill Road.
A fresh appeal comes just days before the second anniversary of his death on November 3.
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Muslim leaders condemned the "heinous and appalling" Westminster terror attack.
Travis Frain is recovering in hospital and has posted a photo to Twitter of Prince Charles by his bedside.
Acting Commissioner Craig Mackey led new policemen and women in paying their respects at a passing-out parade in Hendon, north-west London.