The attacker filmed himself as he lashed out at the homeless victim, 43, in Riley Square, Coventry, yesterday afternoon.
A witness said the man had fallen over drunk and lost his shoe when his attacker approached.
Initially he held out his hand to offer to help him back up, but then he kicked him in the back.
The homeless man ended up going to casualty for treatment to facial injuries following the ordeal.
The footage was put onto the Spotted in Coventry Facebook page yesterday evening, just hours after the assault.
A manhunt is now underway for whoever took the footage that has caused outrage in the area.
Many people recognised the homeless man and say that he does not cause any problems.
West Midlands Police said: ‘Police are investigating an assault on Riley Square in the Wood End area of Coventry just after 11.30am yesterday.
‘A 43-year-old man was approached by a group of up to five men who kicked and pushed him over.
‘Fortunately the man wasn’t seriously hurt and was taken to hospital to be checked over.’
Research from charity Crisis suggested that 8 out of 10 homeless people in England and Wales had suffered some form of violence.
A third of them have been hit or kicked while one in 10 said they have been urinated on while homeless.