CCTV footage has emerged showing an off-duty cop shooting a black man in the chest and head seconds after a road rage fight breaks out.

Delrawn Small, 37, a father-of-two died after being shot by officer Wayne Isaacs on July 4 following a near-miss car accident in Brooklyn.

Witnesses had claimed that Small went over to Isaac's window and 'wailed on his face' before Isaac pulled out his service weapon and shot him, but new footage seems to counter this claim.

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CCTV shows Delrawn Small, 37, being hit almost instantly after walking over to the car window of off-duty cop Wayne Isaacs, who shot him in the chest and head

Small can be seen reeling back before staggering across the road and falling down between two cars

In the footage, obtained by the New York Post, Small can be seen climbing out of his car and walking toward Isaac, who is sitting in his car.

A split second after bending down to look in the window, Small stumbles backward, staggering across the road before collapsing between two parked vehicles.

Another car, sitting parallel to Isaac, speeds off across the junction while pedestrians on the sidewalk run up the street.

Isaac pulls his car forward before slamming on the brakes and getting out. He can then be seen pacing up and down the road on his phone.

Zaquanna Albert, 35, Small's girlfriend, pulls his car across the street before running to his side.

State Attorney General Eric Schneiderman is now investigating the footage to see whether deadly force was justified.

Roger Wareham, lawyer for the Small family, said the footage 'clearly demonstrates the cop lied', adding that Isaac looks down at Small's body 'as if he had just stepped on a roach.'

Wareham told the New York Daily News: 'If the cop's story is obviously false, why haven't they arrested him?'

Isaacs had just finished his shift and was on his way home in his own car when the attack happened.

Small was pronounced dead at the scene but his body remained on the street covered in a plastic sheet for around four hours after the shooting.

The CCTV footage contradicts claims by witnesses and police that Smalls (left and right with girlfriend Zaquanna Albert) had repeatedly hit Isaac before the officer opened fire

Thousands of people took to the streets in New York to protest the killing of Small, Alton Sterling and Philandro Castile, all of whom were shot dead by police in the past week

The footage directly contradicts an earlier account from the owner Touch of Glass, who said his CCTV cameras had captured something very different.

The business owner told the New York Post: 'The video shows the guy coming out of his f***ing car, running up to [the cop's] car, going in the driver's side window and just punching the s*** of this poor cop. Then all of a sudden you see sparks.'

He added that Small 'was wailing on [Isaacs'] face, like pow, pow! He was looking to knock this guy out, punching and punching. Maybe four punches. It was big haymakers.'

Police had put forward a similar account of events, though chief Bill Bratton had urged caution, saying it was too early to tell whether the shooting was justified.

However, construction worker Lloyd Banks, 43, told The Daily News: 'Delrawn and the cop's car almost hit each other. And Delrawn got out of the car and the cop just jumped out and started screaming.

'He just shot him right there on the street. Delrawn was unarmed. His wife and kids were still in the car. They saw everything.'

Small's niece, Zoe Dempsey, 23, told the New York Post: 'We will seek our justice - and get violent if necessary. This is war. I'm from Brooklyn. This is our neighborhood.'

Isaacs has been placed on administrative leave pending the outcome of the investigation, police said. Isaacs was also treated for minor injuries after the incident.

The protests in New York were held just hours before Micah Xavier Johnson opened fire on police at a similar demonstration in Dallas, killing five

Police and community leaders have called for calm in the wake of the shootings, which have caused sharp racial divides in cities across the country

Police said the attack unfolded shortly after Isaacs ended his shift at a Brooklyn precinct and drove away in his civilian clothes.

It wasn't unusual that he was armed - the NYPD allows off-duty officers to carry weapons and to take police action if they encounter criminal activity.

Police say a woman who was riding with Small and their two children, aged five months and 14 years, told investigators that he became enraged after he thought the officer cut him off, then followed the officer's car to the stoplight despite her pleas to calm down and let it go.

They say there was no was back and forth that would have made Isaacs aware that he was being pursued or that Small knew he was an officer.

State assemblyman Charles Barron said Tuesday that he was working with Small's family to demand that authorities hold the officer accountable.

The Brooklyn Democrat and frequent NYPD critic said the officer should have taken steps to defuse the situation with warnings or simply by driving away.