IT took just 90 seconds. In that time, as a terrified mum called for help, her parents and husband were killed and her son shot down just metres away in their family home.

The gunman is then alleged to have turned his shotgun on the police who rushed to her aid and that of a boy, 11, in the Hectorville home at 2.30am yesterday.

With little protection or knowledge of the carnage unfolding inside, the two uniformed officers also fell victim to the gunman - one shot in the face before he was able to return fire and the other injuring his knee as he slipped in the darkness, possibly in a pool of blood.

The shot officer was carried more than 50m by his heroic partner to their patrol car and the woman who raised the alarm was able to escape with the boy.

The gunman then fled, sparking an eight-hour siege.

Police locked down much of the surrounding suburb during the drama and were last night investigating the circumstances and motives for the killings inside the Montacute Rd home.

The family's 39-year-old neighbour, Donato Anthony Corbo, has been charged over the shootings.

Neighbours and witnesses yesterday revealed:

THE 41-year-old victim had emigrated from South Africa with his family about two years ago and his murdered father-in-law, 64, and mother-in-law, 65, were on holidays from South Africa.

CORBO'S father was on a trip to Broken Hill at the time of the shooting.

By late yesterday, police and courts files confirmed:

A WOMAN was removed from Corbo's home by police during the siege.

CORBO was taken to the city watch house and charged with three counts of murder and two counts of attempted murder. He is to face Adelaide Magistrates Court on Monday.

THE youth was in hospital with serious injuries and the wounded police officer was in a serious but stable condition.

POLICE will investigate the circumstances of the response by the two injured patrol officers and whether they were given adequate details of the potential danger they faced.

Neighbour Rob Taddeo heard the commotion outside his home, where the patrol car of the injured officers was abandoned.

He said he saw a police officer carrying his wounded partner on his back to safety.

"There was a police officer carrying another police officer on his shoulders at that stage ... an ambulance turned up and he put the injured officer in the ambulance, and it took off."

Mr Taddeo rang police, who told him to lock himself inside the house.

His wife, Lucie, said she heard yelling.

"There were helicopters circling," she said.

Nick, who lives on Montacute Road almost opposite the victim's home, said he walked outside about 5am to pick the newspaper up off his lawn and was told by a police officer to "get down".

"It was still dark and I tried to pick up the paper, and a policeman said: `Get down' ... I nearly had a heart attack," he said.

"(The policeman) was lying on the lawn and there were about six heavily armed STAR Group officers around the house.

"About 6 o'clock, they knocked on my door and said to stay inside."

Police Deputy Commissioner Gary Burns said it was a "shock" for Adelaide.

"I have the deepest sympathy for the family involved in the shooting, because it is four members of a family who were shot - three generations," he said.

"You don't know what sets these things off.

"It is a huge tragedy ... and we're not sure why, and it happens in suburban Adelaide."

Police were alerted by a frantic call at 2.30am from the woman who survived, saying shots were being fired into their front door on Montacute Road.

The gunman shot at officers after they arrived, the deputy commissioner alleged.

"It will be alleged that the offender fired on police and the officers returned fire," he said.

"One officer was shot in the face."

He is in a serious but stable condition with injuries to his jaw, while a second officer was treated for an injured knee.

Mr Burns said the injured policeman was in an induced coma and would require surgery to his jaw.

"It's a very distressing and traumatic incident for everyone involved," he said.

Another neighbour, Bryan Bennier, 24, said police had briefed the locals.

"It's pretty freaky round this area - this is a nice area - that this happens."

Police asked residents to remain in their homes for much of yesterday, so they could search the crime scene forensically and preserve any evidence.

During the siege, a wide cordon was installed around the alleged shooters home and a no-fly zone overhead was ordered.

Originally published as Horror in Hectorville - three dead