Police have confirmed four people are dead after a shooting in Darwin.

The gunman allegedly went on an hour-long rampage with a shotgun, shooting people at five different locations on Tuesday night.

Four men have been killed and one woman has been injured.

Reports an active shooter in Darwin CBD with up to 20 shots fired and people injured … confusing scenes with tree on fire and roads blocked. pic.twitter.com/4WY2hVE2b3

— Stephanie Zillman (@Steph_Zillman) June 4, 2019

A 45-year-old man is in custody.

Police have confirmed the man is well-known to them and was released from jail on parole in January.

He was also wearing an electronic monitoring bracelet at the time of the shooting.

Police say the man has links to outlaw bikie gangs.

The motivation for the attack is still unknown, but police say it isn’t terrorism-related.

Northern Territory Police Commissioner Reece Kershaw tells Alan Jones the suspect was part of a respected local family.

“He’s well known to many people and that’s why the ripples in the Territory are very intense when this occurs.”

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I have been in contact with Chief Minister Gunner and understand this is not an act of terrorism and a person has been taken into custody. My thoughts are with Territorians and the tight-knit community in Darwin.

— Scott Morrison (@ScottMorrisonMP) June 4, 2019

Witness Joseph Stock tells Ben Fordham about the moment he heard the gunshots.

“You don’t expect to hear gunshots, that’s why you don’t think it is gunshots in Australia.”

Click PLAY to hear the full interview