Four men have been shot dead and a woman injured after a gunman went on a rampage across Darwin's CBD before being arrested by Northern Territory police.
The 45-year-old suspect, who witnesses claim was armed with a pump-action shotgun, started his shooting spree at a motel in Woolner about 5:45pm before travelling in a ute to four other locations, including to the outskirts of the city and back again.
He was arrested after calling NT Police and trying to enter police headquarters in what Police Commissioner Reece Kershaw said may have been an attempt to hand himself in.
The man was known to police, having been released on parole in January, and was wearing an electronic monitoring bracelet.
NT Chief Minister Michael Gunner told a media conference the incident was not believed to be terror related.
The alleged gunman is being held at Royal Darwin Hospital.
"I believe he may have some sort of injury," Commissioner Kershaw said.
NT Health confirmed two people were at the Royal Darwin Hospital in a stable condition.
Witnesses say the man walked into the Palms Motel in McMinn Street while holding a pump-action shotgun and shot at multiple doors.
Multiple witnesses said he was looking for someone called "Alex".
"He shot up every room in that place," one man said.
He said the victims said "they had no idea why he was there, why he was shooting at them, it appeared to be a random attack".
Another witness said he saw the shooter walking calmly though the motel.
"Cops went straight past him, didn't know who he was, he was that calm," he said.
The gunma then fled the scene and remained at large for approximately an hour, with road blocks in place around the city.
Police listed four other crime scenes - among them a man killed at the Buffalo Club, where witnesses said a fight broke out in the carpark with men pulling out a knife and a gun - and Gardens Crescent Road, where residents say a man was shot in the head. That has not yet been confirmed by authorities.
A man was also believed to have been killed at an industrial block on Jolly Street in Woolner.
Another crime scene is the Peter Macauley Centre, which is NT Police headquarters in the outer Darwin suburb of Berrimah.
Prime Minister Scott Morrison, who is in London ahead of D-Day commemorations, condemned the "terrible act of violence".
"I want to extend my deep condolences and sympathy to all the people in the Territory, particularly in Darwin," Mr Morrison said.
"This is a very tight community and I know they will be rocked by these events."
'He shot up all the rooms'
Witness Leah Potter says a woman was shot in the legs at the Palms Hotel before being taken away by an ambulance.
"I was in the carpark [of a neighbouring hotel] when I heard what I thought were fireworks going off, really loud cracking, banging fireworks," she said.
"And then a man came running with a woman in his arms from next door which is the Palms Motel, which is the motel next to my motel, and he just dropped her on the footpath right in front of us.
"I ran and got some towels and wrapped up her legs, she had little holes all in her skin on both her legs and she was bleeding everywhere."
Ms Potter said police were across the road at a Coles Express service station for another matter, "so the boyfriend dropped the bleeding woman in front of us and he ran over to the Coles Express to get the police".
She said the gunman had a pump-action shotgun and ran off down Finniss St towards The Gardens.
"There was lots of blood. She was crying but she was pretty quiet … I think maybe she was in a bit of shock."
Witness Matt James said the woman's boyfriend "told me he opened his door and there was this random gunman standing there who proceeded to unload his rounds on her".
Another witness, John Rose, said he saw the gunman walk into the Palms Motel with "a sawn-off shotgun".
"He shot up all the rooms and he went to every room looking for somebody and he shot them all up, then we saw him rush out, jump into his Toyota pick-up, and rush off."
He said the gunman was calm as he shot up the motel.
"Once he left we went in and found one gentleman, he's over there, we pulled him out," Mr Rose said.
"This lady turned up and started screaming, and we didn't realise there was another person in there… apparently he's dead, he's been shot."