Richard Mannington Bowes, who suffered head injuries and had slipped into comma, was the fifth person to have died in the unrest that dented the David Cameron government's image inside and outside the United Kingdom.
Three British Asians died in Birmingham on Wednesday morning when they were deliberately mowed down by a speeding car, while one man was found shot dead in a car on Croydon on Monday night.
Bowes tried to persuade rioters to stop their activities, but was instead attacked by teenagers who were setting fire to two industrial bins. The policemen who tried to help him were also attacked.
Detective Chief Inspector McFarlane said: "This was a brutal incident that resulted in the senseless killing of an innocent man".
He said the examination of CCTV footage had provided police with a strong suspect: "I know that on seeing these images of him people will be able to identify him. He had been in close proximity to the attack, recording the events on a mobile device".
Mayor of London Boris Johnson paid tribute to him: "There are many villains in this story but also many heroes and I want to pay particular tribute to Mr Bowes. But he has paid a terrible price. I am desperately sorry for him and his family."
The man who was found shot in a car in Croydon was Trevor Ellis, 26. He and his friends were reportedly involved in a row with another group, resulting in a chase involving three cars. Ellis was shot during the pursuit.
The three killed in Birmingham were Haroon Jahan, 21, Shazad Ali, 30, and Abdul Musavir, 31. The West Midlands Police said two boys, aged 16 and 17, and a man, 26, had been arrested on suspicion of murder.
Unveiling vigorous measures to tackle the riots, Premier David Cameron onThursday promised extra powers to police to quell the violence. Tough-talking Cameron warned rioters that they will be tracked down, charged and punished for what they have done.
"We will track you down, we will find you, we will charge you, we will punish you. You will pay for what you have done," he said.
"We will not allow a violent few beat us," Cameron told a rare recall of Parliament to tackle the extraordinary situation.