A 17-year-old has been sentenced to eight years for killing pensioner Richard Mannington Bowes during the London riots in 2011.
Darrel Desuze, of Hounslow, west London, pleaded guilty at Inner London crown court to the manslaughter of Bowes, 68.
Desuze punched the pensioner to the ground as he tried to stamp out a fire in a road in Ealing, west London, on 8 August. The victim suffered brain damage after his head hit the pavement and he died three days later.
Desuze's mother Lavinia, 31, was jailed at the same court for 18 months for perverting the course of justice by cutting up his clothes to destroy the evidence. Desuze was named in court after an order banning his identification was lifted by a judge.
Mr Justice Saunders said he took into account in passing sentence the teenager's previous pleas of guilty to burglary and violent disorder at William Hill, Tesco Express, Blockbuster and Fatboys Thai restaurant on the same night as the attack on Bowes.
The judge said Desuze "played a full part in the violence". He could be seen on CCTV smashing windows, looting shops, throwing missiles at police and wheeling rubbish bins into the street so they could be set on fire.
Saunders said most people were afraid to go out, and those caught up in the violence would have been "terrified".
"One person who was not terrified to be out and was not prepared to be forced off the streets was Richard Mannington Bowes," he said.
CCTV footage showed Bowes moving among the rioters and attempting to prevent bin fires from spreading.
"The death of Mr Bowes was pointless and unnecessary and it became for the public one of the most, if not the most, shocking event of the riots in London," Saunders said.
Desuze was filmed on CCTV wearing a distinctive top saying marked "Robbers and Villains" during the disturbances.
The judge said that on August 13 his mother cut up his clothing and dumped it in a bin at midnight.
"I do feel, as most people would, some sympathy for Lavinia Desuze," the judge said.
"On the jury's verdict, even though she committed a very serious offence, she did so to protect her young son to whom she had given birth when she was only 14 and who she had looked after as a single mother for most of his life.
"I accept that the instinct of a mother to protect her child is a very powerful one."