IPCC to reinvestigate Edric Kennedy-Macfoy's claims that police abused and assaulted him before shooting him with a stun gun

A racism complaint by an off-duty black firefighter who claims he was abused, assaulted and shot with a stun gun after trying to help police is being reinvestigated, after the police watchdog took the unprecedented step of rejecting a police report on the case.

Edric Kennedy-Macfoy, 29, has accused police of behaving like "wild animals", dragging him from his car and subjecting him to a violent attack that culminated in him being shot with a Taser.

He had approached the officers in Harrow, north London, to help identify a young man who had hurled a rock at a police van. He has said he was shocked when officers suddenly turned on him, and believes he was targeted because of his skin colour.

The Metropolitan police investigated Kennedy-Macfoy's complaint internally, with supervision from the Independent Police Complaints Commission (IPCC). Its conclusions about the incident, contained in a report compiled by the force's complaints department, was handed over to the IPCC this month.

On Thursday the IPCC revealed it had rejected those findings and ordered a new and fully independent inquiry. It is believed to be the first time in the history of the IPCC that a decision has been taken to wholly reject the conclusions of an internal police report and initiated a fresh investigation.

"After all these months I am still waiting to see if any officers will be prosecuted for what happened to me," Kennedy-Macfoy said. "I hope the IPCC will conduct a thorough investigation. Its failure to take this step at the outset means that it has a lot of work to do to restore my faith in this process."

Kennedy-Macfoy was driving through Harrow at 3.30am on 4 September 2011 when he saw a young man hurl a missile at a police van. After noting a description of the young man, Kennedy-Macfoy – who also trained as a police constable – flagged down the van driver and approached a line of officers to pass on the information.

He was wearing a three-piece pinstriped suit and driving a white Audi when he encountered the police, who were forming a roadblock. He alleges that officers suddenly turned on him, hurling abuse, charging at his car and grabbing him "viciously" through the windows.

He says he was dragged from the car and in the ensuing melee the officers repeatedly encircled him and shouted profanities. Kennedy-Macfoy said he replied calmly and showed his palms to the officers, telling them: "Listen guys, I haven't done anything wrong. I'm a firefighter – I work with you lot and I just want to explain something. I've showed no aggression toward any of you." He was eventually shot with a Taser stun gun.

Kennedy-Macfoy was found not guilty in February last year of obstructing police. During a two-day trial at Brent magistrates court, the police officer who discharged the weapon conceded he did not warn Kennedy-Macfoy that he was about to be shot – an apparent contravention of Home Office guidelines.

Another officer present on the night, Inspector David Bergum, said his officers had been in a "stressful" situation, dealing with a group of partygoers who were throwing missiles at them.

He said of Kennedy-Macfoy: "I couldn't say he was anything to do with the party. The party was all black. He was black. He had driven through the cordon. I had to do a quick risk assessment."

In April last year the Guardian revealed how the case was being treated as a potentially racially motivated incident after details of the inspector's comments in court were sent to the Met police. The case was then referred to the IPCC, which announced it would supervise the investigation, deciding against conducting a full, independent inquiry.

Reversing that decision on Thursday, the IPCC commissioner Jennifer Izekor said the watchdog would thoroughly review the evidence already obtained and "conduct further inquiries" as necessary.

"We need to be satisfied that Mr Kennedy-Macfoy's serious allegations have been comprehensively examined," she said. "We have informed Mr Kennedy-Macfoy's solicitors that our independent investigation is under way and will be conducted as quickly as possible."

Kennedy-Macfoy, who was once set to become a police officer but left the Hendon police training academy after his mother became ill with cancer in 2005, has said he hopes his complaint will make police think twice before stereotyping black men.

Although the firefighter worked alongside police "almost every day" for six years, and has a number of close friends in the police, he said he had struggled to return to work since the experience.

His lawyer, Shamik Dutta, of Bhatt Murphy solicitors, said: "This is a vote of no confidence by the IPCC in the Met's ability to investigate its own officers. Although we have not been shown the Met's internal findings, the fact the IPCC has taken the highly unusual step of independently investigating the case at this late stage speaks volumes about the standard of the police's own initial inquiry."

• Inspector Burgum denies any involvement in or responsibility for the abuse, assault or tasering of Edric Kennedy-Macfoy or that this attack was racially motivated. A further article was published on 25 November 2014 here.