A man has been killed and his partner seriously injured after her former partner allegedly doused the couple in petrol and set their home alight in South Australia.

Don Couzens, 65, had travelled from Mildura to Redhill in the state’s Mid North to spend the weekend with his partner, Jenni Henderson, when the alleged domestic violence attack unfolded about 7pm on Saturday.

WATCH THE VIDEO ABOVE: Man killed in alleged fire attack in Redhill

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Witnesses said the couple were enjoying a quiet night at the Hope St property when Henderson’s former partner arrived.

Police allege the man deliberately set the home alight.

Footage obtained by 7NEWS shows the house engulfed in flames as the fire tore through the property.

The Redhill home was engulfed in flames. Credit: 7NEWS

Henderson managed to escape the burning home and ran across the road to a neighbour for help.

Neighbour Rachel Manning said Henderson had suffered horrific burns.

“They were both covered in petrol. She was burnt from the waist down terribly,” Manning said.

“So I’ve put her in the water and just done what we could.”

Another neighbour, James Winstone, ran towards the inferno after hearing desperate cries for help.

“I came running down to do what I can and there was someone in the front door, so I dragged him out,” he said.

“I just had to save someone.”

Don Couzens, 65, had travelled to Redhill to spend the weekend with his partner when he was killed. Credit: Facebook

But the man Winstone pulled from the burning home was the 63-year-old who police allege had started the blaze.

Couzens, however, remained trapped inside.

His body was found after the fire was extinguished.

Manning said Couzens and Henderson had only recently begun their relationship and described the pair as deeply in love.

“He was really in love with her,” she said.

“They were just smitten with each other. It’s only been a new recent thing.”

Jenni Henderson suffered serious burns in the alleged attack. Credit: Facebook

The alleged offender and Henderson were both airlifted to the Royal Adelaide Hospital with serious burns.

Henderson was in a stable condition, while the 63-year-old man was being treated for life-threatening injuries.

Major Crime and forensic officers joined local detectives at the charred property on Sunday as investigations continued.

Police expect the Wirrabara man to be charged with murder, attempted murder and arson once he is medically fit.

Anyone with information, CCTV or dashcam footage is urged to come forward.

If you or someone you know is impacted by sexual assault, domestic or family violence, call 1800RESPECT on 1800 737 732 or visit 1800RESPECT.org.au.

In an emergency, call 000.

Advice and counselling for men concerned about their use of family violence: Men’s Referral Service, 1300 766 491