A special prosecutor for the state of Georgia in United States said on Thursday that evidence in the killing of Ahmaud Arbery shows that the young black man was repeatedly boxed in by two pickup trucks as he desperately tried to escape.

The lead Georgia Bureau of Investigation agent in the case testified that the white driver of the first pickup, Travis McMichael, finally got out and shot Arbery in the chest, the first of three shots with a pump-action shotgun that sent Arbery staggering and falling onto the road, mortally wounded.

Agent Richard Dial said the driver of the second pickup truck, William “Roddie” Bryan, said he heard the gunman say a racist epithet as he stood over Arbery’s body before police arrived.

Special prosecutor Jesse Evans said Arbery “was chased, hunted down and ultimately executed”.

The evidence was presented to support murder charges against McMichael and his father as well as Bryan.

It challenges the claims of self-defense that have been raised by the gunman and his father, Greg McMichael. It also could factor into a federal investigation into whether hate crime charges are warranted.

Lawyers for the defendants and the state acknowledged in court the extraordinary context for the hearing, following a week of angry protests in the US over law enforcement biases against black victims.

Arbery was killed on February 23 after the father and son armed themselves and gave chase when they spotted the 25-year-old black man running in their neighbourhood just outside the port city of Brunswick. Bryan said he spotted them driving by and joined the chase, Dial said.

It wasn’t until May 7 that those men — Greg McMichael, 64, and Travis McMichael, 34 — were charged with felony murder and aggravated assault. The McMichaels’ arrests came two days after cellphone video of the shooting leaked online and stirred a national outcry.

Bryan, 50, filmed the video. He also was arrested and charged with felony murder and illegally using a vehicle to try to confine and detain Arbery.

Largely peaceful protests following the deaths of George Floyd in Minneapolis, Breonna Taylor in Louisville, Kentucky, and Arbery have led to outbreaks of violence in many larger cities, including Atlanta.

Greg McMichael told police after the shooting in February that he suspected Arbery of committing break-ins in the neighbourhood. He said Arbery attacked his son before being shot.

Arbery’s family has said that he was merely out jogging. The former high school football player ran to stay in shape and lived less than 3.2 kilometres away from the subdivision where he was killed.

His mother said he planned to start technical college in the fall to become an electrician.