The alleged gunman responsible for killing four men and injuring one woman in Darwin on Tuesday was stopped by police for speeding just hours before he went on the rampage.

Northern Territory police commissioner Reece Kershaw said officers apprehended the suspect, Ben Hoffman, 45, on the Arnhem Highway for doing 94km/h in an 80 zone at about 10.52am.

READ MORE: Second Darwin mass shooting victim revealed

Accused mass murderer Ben Hoffman leaves hospital after surgery for knife wounds. (9News)

“We have reviewed the body-worn video and he was not displaying any adverse behaviour to reveal he was under the influence of anything,” Comm Kershaw told reporters today.

“Nothing out of the ordinary was observed by police officers.”

Ben Hoffmann has been named as the alleged gunman behind the Darwin shooting rampage. (Facebook)

However, when apprehended by General Duties Officers and Territory Response Group Officers at the intersection of McMinn and Daly Streets nearly eight hours later at 6.44pm, he was allegedly displaying behaviour consistent with being under the influence of an intoxicating substance.

By that time four people lay dead in four different crime scenes around the city.

Comm Kershaw said he was awaiting toxicology reports.

“It’s highly likely it will be methamphetamine, also known as ice,” he said.

Police arrest the suspected gunman at the intersection of McMinn and Daly Streets (ABCSupplied)

Police also said investigations have revealed the knife and ammunition allegedly used by the accused were not obtained illicitly, with a well-known associate allegedly responsible for giving him the weapons.

“That person has been spoken to and, obviously, we are looking at all avenues in relation to that individual,” he said.

Comm Kershaw said police believe the 52-year-old male killed at Jolly Street and the 57-year-old male murdered at the Buff Club were both known to the accused.

He added police were following lines that the dispute might have been over a woman or related to drugs. Commissioner Kershaw said 118 police were working on the case.

“The suspect has undergone surgery for what appears to be knife wounds that were sustained prior to him being apprehended by police,” he said.

“He's been cleared fit for custody and has been transferred, as we speak now, to the Darwin watch-house.

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“He is being formally interviewed by Major Crime detectives today. It is also anticipated that later today he will be charged with four counts of murder.”

Once the alleged is moved to Darwin Correctional Centre, he will be placed in high security and will be isolated from the rest of the prison population. As he is classified as "high risk", there will be an individual management plan aligned to the individual.

Comm Kershaw added police had “spoken to him for 55 minutes under caution, noting that he is represented legally”.

Known as “Hoffy” to those closest to him, the alleged gunman had been released from prison on parole in January after being sentenced to six years’ imprisonment with a non-parole period of four years, police revealed today, without naming the suspect.

Hoffman was released on parole with 23 strict conditions, which included a requirement for him to wear an electronic monitoring bracelet that was not removed before yesterday’s alleged shooting.

Nine ballistic and forensic experts were flown in from Sydney to assist with the investigations.

Meanwhile, the alleged gunman’s brother, Clinton Hoffmann, a well-known local businessman in the Darwin area, said his family was “shocked” and “distressed” over Tuesday night’s events which left four people dead.

“There is public speculation that the offender was my brother Ben Hoffmann,” Mr Hoffmann said in a statement.

“It is important at this time to allow the proper and thorough investigation of these matters by the Northern Territory police and I do not wish to do or say anything that might interfere with or compromise that investigation.

Taxi driver Hassan Baydoun has been identified as a victim of Hoffman's alleged rampage. (Supplied)

“Having said that, I wish to express my, and my family’s deepest condolences to all of those affected by those events including the families and friends of those who tragically lost their lives, the injured woman and those who came into harm’s way.

“We are as shocked and distressed about these events as the community around us.

“In the fullness of time, it may be appropriate to say more. At present, I thank my friends and colleagues for their understanding and their expression of support, especially to me, my mother and other members of my family.

“In the interests of allowing legal matters to properly run their course, I will not be making a further public statement on these matters at this time.”

Details of his record emerged as the first victim was named as taxi driver Hassan Baydoun , originally from Lebanon.

9News understands Mr Baydoun maybe have been living at the Palms Motel.

Mr Baydoun had been driving his taxi but returned home to his studio apartment in McMinn St yesterday evening for a meal break.

Mr Baydoun had been working for Blue Taxis, and it mourned the loss of one of its “beloved” employees.

READ MORE: Immediate review into parolees ordered after Darwin shooting

“Our Company is heartbroken and his colleagues are in a state of shock. This is not what our city stands for. Someone shot having a meal break while going about their own business.

“We pray that we never have to witness anything like this ever again.

“We mourn him and honour him. Our sincerest condolences and prays to his family and friends RIP, Hassan.”

With more than 100 police now trying to determine what led to the tragic events, the police have released a timeline of events.

Police cordon off Palms Motel after the shooting (AAP Image/Michael Franchi). (AAP)

Police were first notified of the incident at 5.45pm on Tuesday when they received reports of a man armed with a shotgun firing rounds in the Darwin CBD.

The suspect was first traced to the Palms Motel in Finnis St at about 5.50pm, searching for a person known to him.

He threatened two people at the location prior to shooting a 22-year-old female who sustained non-life threatening injuries to her legs. She is currently in hospital in a stable condition.

A 33-year-old male was shot at the same location, and has died at the scene.

At 5.50pm, the alleged offender attended a residence in Gardens Hill Crescent and fatally shot a 75-year-old male.

At 5.59pm the alleged offender attended the Buff Club in Stuart Park, where he fatally shot a 57-year-old male.

The alleged offender then attended an address in Jolly Street, Woolner, where he fatally shot a fourth person, a 52-year-old male.

At 6.24pm, he drove to the Peter McAulay Centre in Berrimah and unsuccessfully tried to enter the police station, before leaving the area. At this stage it is unclear as to why he was trying to enter the police station.

He has then contacted the Joint Emergency Services Communications Centre, requesting police protection.

The Buffalo Club in Darwin was one of the crime scenes. (Nine)

The alleged offender was apprehended by General Duties Officers and Territory Response Group Officers at the intersection of McMinn and Daly Streets at 6.44pm Tuesday.

A firearm was seized during the arrest. Investigations are ongoing as to how he came into possession of the weapon.

“There is a police investigation, there will be a court case, there will be a coronial,” Northern Territory Chief Minister Michael Gunner said at a press conference.

“Police will have an independent review of the incident and details will be advised later. We’ve asked for a detailed report from the Parole Board of the alleged offered and directed an immediate review of the 103 people currently on parole.”

Officers have confirmed the weapon allegedly used, a pump-action 12-gauge shotgun, was a prohibited firearm that “may have been stolen as far back as 1997”.

Police cordon off a block of units where a person was shot by a gunman in the suburb of The Gardens. (AAP)

NT Corrections Commissioner Scott McNairn said the man was released on parole in January this year and had only received one mire breach for breaking his curfew by less than an hour.

“[He] was subject to a 14-day custodial sentence as a result,” he said. “He was subject during his time on parole to random drug testing, all of which returned negative tests. His last drug test was on May 21, 2019.”

Mr McNairn said the accused had broken his curfew period – requiring him to be home between 10pm and 6am – the previous evening.

“The offender left home during his curfew to attend the Royal Darwin Hospital to seek medical treatment and this is a permitted reason to leave home during a curfew period. He contacted Community Corrections to advise them.”

Police at the intersection of Stuart Highway and McMinn Street where Ben Hoffman was apprehended. (AAP)

Earlier, witness John Rose told 9News how he saw the alleged gunman enter and exit the Palms Motel multiple times and fire at least 15 shots.

He heard "two loud bangs" which he initially thought were from fire crackers.

Mr Rose said while he and his neighbours were calling police when the suspected gunman exited the motel.

Leah Potter also witnessed police rushing to the scene where one man had been shot dead.

"A man was riding his bike and the policeman stopped him and commandeered the bike and rode down Finnis Street," she told Today.

CCTV footage captured one of the cars used by the gunman. They want to speak to anyone who might have seen any of the cars he used during the day. (Nine)