A postmortem will held today on a 19-year-old man who was shot dead in Clapton on Saturday.
A second man was also hurt in the attack but is in a stable condition.
No arrests have yet been made and the police are appealing for any information.
More top news
Officers were given the touching letter at Brixton Station while they were on a reassurance patrol after yesterday's attack
The 52-year-old had previous convictions for violence but was not on the anti-terror watchlist.
In a statement Charlton Athletic said: Keith was a true hero who will be greatly missed by all the Charlton family and everyone at the club.