A boy suspected of a mass shooting in North Carolina on Thursday began the rampage by fatally shooting a relative at home, police have said.

Five people including an off-duty police officer were killed and two injured in the attack in Raleigh.

The 15-year-old suspect is in a critical condition in hospital, but it is not clear how he was injured.

The Gun Violence Archive says there have been 533 mass shootings (four or more shot) in the US this year.

Thursday's attack unfolded in a residential neighbourhood near the Neuse River Greenway, a popular trail on the outskirts of the state capital.

The unnamed suspect's motive is yet to be established, said police. He is white, and the victims were all of different races.

After shooting a relative at home, the boy went out into the street and shot two women in the neighbourhood, Raleigh Police Chief Estella Patterson said on Friday morning.

The suspect then allegedly ran towards the local river trail, fatally shooting 29-year-old police officer Gabriel Torres, who was on his way to work. 

Once on the trail the attacker killed two more people and wounded two others, said the police chief.

A nearby primary school was locked down and two community centres were pre-emptively evacuated.

"My heart is heavy, because we don't have answers as to why this tragedy occurred," Chief Patterson said.

The shooting - which spanned over two miles - began just after 17:00 EDT (21:00 GMT) on Thursday.

A police dog tracked the suspect to a shed, where he was taken into custody about four-and-a-half hours later.

The two wounded victims included another police officer, Casey Clark, 33, who has since been released from hospital, and a 59-year-old woman, who was in a critical condition.

Along with Officer Torres, the deceased victims were identified by officials as Nicole Connors, 53, Susan Karnatz, 49, Mary Marshall, 34, and James Thompson,16.

Ms Connors' husband told the Associated Press news agency she had been chatting to a neighbour on the porch when she was shot. Ms Marshall was walking her dog, Scruff, her sister told NBC.

Ms Karnatz's husband, Tom, posted a tribute to the mother-of-three on Facebook, writing: "We had plans together for growing old. Always together."

Wake County District Attorney Lorrin Freeman said on Friday the teen suspect would be charged as an adult.

More than 34,000 people have died in shootings in the US in 2022, more than half of which were from suicide, according to the Gun Violence Archive website.

"We must stop this mindless violence in America," said North Carolina Governor Roy Cooper, a Democrat, after the shooting. "We must address gun violence. We have much to do, and tonight we have much to mourn."/BBC