Police say anyone who witnessed the shooting, or has any information should contact detectives on 0208 358 0200, or Crimestoppers anonymously on 0800 555 111.
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Several passers-by can be seen apparently reacting to the incident in the footage.
Victims ranging from age three to 60 will be remembered as part of six special hearings dedicated to those who lost their lives.
"I do not accept the allegation that I have brought the Labour Party into disrepute", said Livingstone.