Darwin shooting witnesses describe chaos and terror

Witnesses of the shooting in Darwin which left four people dead and one injured have spoken about the horror they saw.

Matt Janes and Leah Potter were both outside the Palms Motel, the first location where the gunman opened fire.

"A guy came running up to me with this woman in his arms, she was screaming she'd been shot and he was saying he had no idea why this shooter was approaching them," Janes told Sunrise on Wednesday.

"He just placed her at my feet. They were both hysterical," he continued.

He said he wrapped the woman's legs in a blanket to stem the bleeding, and Potter helped him to move her into a nearby police car for protection.

Janes said he didn't see the weapon, but knew the situation was dire.

"I didn't see [the gun] but I saw the damage, buckshot injuries all over her legs."

Janes described the shooting as "surreal in all aspects".

"We don't expect that here, or anywhere. That he could get out on parole being the dangerous person that he is, is shocking in itself, [and] it's hard to believe someone would have these thoughts and carry out these actions."

The gunman then moved across Darwin, visiting three other locations and killing a man at each, reports 7 News.

He was arrested outside a block of flats an hour after he first opened fire.

The alleged gunman is known to police, and was wearing an electronic ankle monitor to track his movements.

AAP reports he is a member of a motorcycle gang, with a lengthy criminal history.