The youth, who cannot be named because of his age, punched Richard Mannington Bowes, knocking him to the ground as he was trying to put out a fire during the riots last summer.
Mannington Bowes suffered brain damage as a result of impact on the ground, and died in hospital on August 11.
His killer admitted manslaughter when he appeared at Inner London crown court. He also pleaded guilty to violent disorder during the London riots, having previously admitted burglary at William Hill, Tesco Express, Blockbusters and Fatboys Thai restaurant on August 8.
Mannington Bowes was set upon on the third night of the London riots when he was trying to extinguish a fire in a supermarket bin near the Arcadia Shopping Centre in Ealing, west London.
A picture of him lying face down in a pool of blood came to represent the wilful callousness and destruction seen during the London riots.
Mannington Bowes’s sister, Anne Wilderspin, who had not seen her brother for 30 years, said the ordeal had been an emotional rollercoaster.
“I don’t really feel anything at the moment. I am overwhelmed by the last 24 hours and just feel a bit stunned. I am trying to come to terms with everything that’s been going on,” she said.
Ealing council has launched an appeal in the victim’s memory, to help those affected by the riots in Ealing.
Council leader Julian Bell said Mannington Bowes had died trying to protect the area in which he lived. “Although I did not know
Mr Mannington Bowes, what I know about him I liked and my thoughts are with his family and friends. He was out on Monday night trying to protect the area where he lived and standing up for what is right. Sadly, someone who will clearly never share these values murdered him as a mob rampaged through our normally quiet streets.”
The teenager still faces a murder charge and will appear in court again on Tuesday.