A police officer Tasered her force's black race relations adviser in the face after mistaking him for a wanted man.
Grandfather Judah Adunbi, 63, cried out and collapsed after being shocked with the 50,000-volt immobilising weapon.
It happened during a row with police who demanded that he identify himself as he returned home from walking his dog, the Daily Mail reported.
After refusing to tell the officers his name, he was pulled into the street and Tasered in an incident caught on camera by a neighbour.
It is particularly embarrassing for Bristol police because Mr Adunbi is a founding member of an advisory group seeking to create better relations between the black community and the force.
The Independent Police Complaints Commission has been alerted and the officer who discharged the Taser suspended from carrying one.
Mr Adunbi, who revealed he was singled out in another case of mistaken identity a decade ago, said last night: "The first time round it could have been an accident - but a second time, that's a racist attack.
"To know that I'm one of the founder members of the independent advisory group, created some years ago to improve the relationship between the Afro-Caribbean community and the constabulary, and to be treated like this, it's difficult."
Mr Adunbi, who said he has suffered sleepless nights since the incident, was Tasered outside his home in the Easton area of the city as he stood with his dog, Hazel.
The video recorded by a neighbour shows police approach and ask his name. He replies: "I'm not telling you my name. I've done no wrong."
As he faces the two officers, he says: "If you Taser me you'll probably kill me and it's going to cost you a hell of a lot."
A woman officer then discharges the weapon at him from close range, shouting "Taser, Taser, Taser". Mr Adunbi falls backwards on to the road.
As he recovers his senses, he shouts: "I've been murdered here." A neighbour adds: "That was totally unnecessary."
Mr Adunbi was taken to hospital, then to a police station where he was charged with assaulting a police officer and disorderly behaviour. The charges were dropped.
He said later: "It's a grace of God that I'm still alive - the way I fell on the back of my head. I was paralysed. I thought they were taking my life."
Chief Supt Jon Reilly, of Avon and Somerset Police, said he had a "constructive" meeting with Mr Adunbi and the force took community concerns about the incident seriously.